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Статті в журналах з теми "Kelvin wave angle"
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Pethiyagoda, Ravindra, Scott W. McCue, and Timothy J. Moroney. "What is the apparent angle of a Kelvin ship wave pattern?" Journal of Fluid Mechanics 758 (October 9, 2014): 468–85. http://dx.doi.org/10.1017/jfm.2014.530.
Повний текст джерелаАнотація:
AbstractWhile the half-angle which encloses a Kelvin ship wave pattern is commonly accepted to be 19.47°, recent observations and calculations for sufficiently fast-moving ships suggest that the apparent wake angle decreases with ship speed. One explanation for this decrease in angle relies on the assumption that a ship cannot generate wavelengths much greater than its hull length. An alternative interpretation is that the wave pattern that is observed in practice is defined by the location of the highest peaks; for wakes created by sufficiently fast-moving objects, these highest peaks no longer lie on the outermost divergent waves, resulting in a smaller apparent angle. In this paper, we focus on the problems of free-surface flow past a single submerged point source and past a submerged source doublet. In the linear version of these problems, we measure the apparent wake angle formed by the highest peaks, and observe the following three regimes: a small Froude number pattern, in which the divergent waves are not visible; standard wave patterns for which the maximum peaks occur on the outermost divergent waves; and a third regime in which the highest peaks form a V-shape with an angle much less than the Kelvin angle. For nonlinear flows, we demonstrate that nonlinearity has the effect of increasing the apparent wake angle so that some highly nonlinear solutions have apparent wake angles that are greater than Kelvin’s angle. For large Froude numbers, the effect on apparent wake angle can be more dramatic, with the possibility of strong nonlinearity shifting the wave pattern from the third regime to the second. We expect that our nonlinear results will translate to other more complicated flow configurations, such as flow due to a steadily moving closed body such as a submarine.
2
Liang, Hui, and Xiaobo Chen. "Viscous effects on the fundamental solution to ship waves." Journal of Fluid Mechanics 879 (October 1, 2019): 744–74. http://dx.doi.org/10.1017/jfm.2019.698.
Повний текст джерелаАнотація:
The fundamental solution to steady ship waves accounting for viscous effects (the viscous-ship-wave Green function) is investigated within the framework of the weakly damped free-surface flow theory. An explicit expression of the viscous-ship-wave Green function is firstly derived, and an accurate and efficient technique is described to evaluate the Green function via decomposing the free-surface term into the local-flow component and wave component. To delve into the physical features of the viscous-ship-wave Green function, the asymptotic approximations in the far field due to Kelvin, Havelock and Peters are presented for the flow-field point located inside, at and outside the Kelvin wedge. In addition, uniform approximations to the wave component based on the Chester–Friedman–Ursell (CFU) approximation and the Kelvin–Havelock–Peters (KHP) approximation are carried out. Both numerical evaluation and asymptotic approximations show that the singular behaviour is eliminated and the divergent waves associated with large wavenumbers leading to rapid oscillations are severely damped when viscous effects are accounted for. In addition, viscous effects also alter the apparent wake angle associated with the wave pattern created by a high-speed translating source, and the apparent wake angle is dependent on both $\mathscr{U}^{-1}$ and $\mathscr{U}^{-2}$, where $\mathscr{U}$ is the translating speed of the source.
3
Fang, M. C., R. Y. Yang, and I. V. Shugan. "Kelvin Ship Wake in the Wind Waves Field and on the Finite Sea Depth." Journal of Mechanics 27, no. 1 (March 2011): 71–77. http://dx.doi.org/10.1017/jmech.2011.9.
Повний текст джерелаАнотація:
ABSTRACTA kinematics model of the ship wake in the presence of surface waves, generated by wind is presented. It was found that the stationary wave structure behind the ship covered a wedge region with the 16.9° half an angle at the top of the wake and only divergent waves are present in a ship wake for co propagating wind waves. Wind waves field directed at some nonzero angle to the ship motion can cause essential asymmetry of the wake and compressing of its windward half. The extension of Whitham-Lighthill kinematics theory of ship wake for the intermediate sea depth is also presented. The ship wake structure essentially depends from the Froude (Fr) number based on the value of the sea depth and ship velocity. For Froude number less than unit both longitudinal and cross waves are presented in the wake region and Kelvin wake angle increased with Fr. For Fr > 1 wake angle decreased with Froude number and finally only divergent waves are presented in the very narrow ship wake.
4
ZHU, QIANG, YUMING LIU, and DICK K. P. YUE. "Resonant interactions between Kelvin ship waves and ambient waves." Journal of Fluid Mechanics 597 (February 1, 2008): 171–97. http://dx.doi.org/10.1017/s002211200700969x.
Повний текст джерелаАнотація:
We consider the nonlinear interactions between the steady Kelvin waves behind an advancing ship and an (unsteady) ambient wave. It is shown that, for moderately steep ship waves and/or ambient waves, third-order (quartet) resonant interaction among the two wave systems could occur, leading to the generation of a new propagating wave along a specific ray in the Kelvin wake. The wave vector of the generated wave as well as the angle of the resonance ray are determined by the resonance condition and are functions of the ship forward speed and the wave vector of the ambient wave. To understand the resonance mechanism and the characteristics of the generated wave, we perform theoretical analyses of this problem using two related approaches. To obtain a relatively simple model in the form of a nonlinear Schrödinger (NLS) equation for the evolution of the resonant wave, we first consider a multiple-scale approach assuming locally discrete Kelvin wave components, with constant wave vectors but varying amplitudes along the resonance ray. This NLS model captures the key resonance mechanism but does not account for the detuning effect associated with the wave vector variation of Kevin waves in the neighbourhood of the resonance ray. To obtain the full quantitative features and evolution characteristics, we also consider a more complete model based on Zakharov's integral equation applied in the context of a continuous wave vector spectrum. The resulting evolution equation can be reduced to an NLS form with, however, cross-ray variable coefficients, on imposing a narrow-band assumption valid in the neighbourhood of the resonance ray. As expected, the two models compare well when wave vector detuning is small, in the near wake close to the ray. To verify the analyses, direct high-resolution simulations of the nonlinear wave interaction problem are obtained using a high-order spectral method. The simulations capture the salient features of the resonance in the near wake of the ship, with good agreements with theory for the location of the resonance and the growth rate of the generated wave.
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THIEBAUT, S., and R. VENNELL. "Resonance of long waves generated by storms obliquely crossing shelf topography in a rotating ocean." Journal of Fluid Mechanics 682 (July 7, 2011): 261–88. http://dx.doi.org/10.1017/jfm.2011.221.
Повний текст джерелаАнотація:
The oceanic forced wave beneath a moving atmospheric disturbance is amplified by Proudman resonance. When modified by the Earth's rotation this classical resonance only occurs if the disturbance time scale is smaller than the inertial period. With or without Coriolis effects, free transients generated by storm forced waves obliquely crossing step changes in water depth at particular angles are shown to resonate by exciting a range of long barotropic free waves. Rotationally influenced slow atmospherically forced waves crossing a vertical coast at a critical angle lead to a form of subcritical resonance, which occurs only when the component of the disturbances' phase velocities along the coast matches that of a free Kelvin wave (KW). In a rotating ocean, transients generated by disturbances crossing a step at a particular angle are shown to excite a free double Kelvin wave (DKW). This new type of resonance only occurs for sufficiently large steps and disturbances with time scale greater than the inertial period. A storm crossing a step shelf can result in the excitation of an infinite set of edge waves, a single KW, a unique DKW and a first-mode continental shelf wave, depending on the topography and the disturbance time scale, translation speed and incident angle. The study of resonances and wave mode excitations generated by storms crossing a coast or a continental shelf may contribute to understanding how a particular combination of the storm characteristics can result in destructive coastal events with time scales encompassing the typical meteotsunami period band (tens of minutes) and storm surges with periods of several hours or days.
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Gnevyshev, Vladimir, and Sergei Badulin. "Wave Patterns of Gravity–Capillary Waves from Moving Localized Sources." Fluids 5, no. 4 (November 24, 2020): 219. http://dx.doi.org/10.3390/fluids5040219.
Повний текст джерелаАнотація:
We study wave patterns of gravity–capillary waves from moving localized sources within the classic setup of the problem of ship wakes. The focus is on the co-existence of two wave systems with opposite signatures of group velocity relative to the localized source. It leads to the problem of choice of signs for phase functions of the gravity (“slow”) and capillary (“fast”) branches of the dispersion relation: the question generally ignored when constructing phase patterns of the solutions. We detail characteristic angles of the wake patterns: (i) angle of demarcation of gravity and capillary waves—“the phase Mach” cone, (ii) angle of the minimal group velocity of gravity–capillary waves—“the group Mach” cone, (iii, iv) angles of cusps of isophases that appear after a threshold current speed. The outer cusp cone is naturally associated with the classic cone of Kelvin for pure gravity waves. The inner one results from the effect of capillarity and tends to the “group Mach” pattern at high speeds of current. Amplitudes of the wave patterns are estimated within the recently proposed approach of reference functions for the problem of propagation of packets of linear dispersive waves. The effect of shape is discussed for elliptic reference sources.
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Tings, Björn. "Non-Linear Modeling of Detectability of Ship Wake Components in Dependency to Influencing Parameters Using Spaceborne X-Band SAR." Remote Sensing 13, no. 2 (January 6, 2021): 165. http://dx.doi.org/10.3390/rs13020165.
Повний текст джерелаАнотація:
The detection of the wakes of moving ships in Synthetic Aperture Radar (SAR) imagery requires the presence of wake signatures, which are sufficiently distinctive from the ocean background. Various wake components exist, which constitute the SAR signatures of ship wakes. For successful wake detection, the contrast between the detectable wake components and the background is crucial. The detectability of those wake components is affected by a number of parameters, which represent the image acquisition settings, environmental conditions or ship properties including voyage information. In this study the dependency of the detectability of individual wake components to these parameters is characterized. For each wake component a detectability model is built, which takes the influence of incidence angle, polarization, wind speed, wind direction, sea state (significant wave height, wavelength, wave direction), vessel’s velocity, vessel’s course over ground and vessel’s length into account. The presented detectability models are based on regression or classification using Support Vector Machines and a dataset of manually labelled TerraSAR‑X wake samples. The considered wake components are: near‑hull turbulences, turbulent wakes, Kelvin wake arms, Kelvin wake’s transverse waves, Kelvin wake’s divergent waves, V‑narrow wakes and ship‑generated internal waves. The statements derived about wake component detectability are mainly in good agreement with statements from previous research, but also some new assumptions are provided. The most expressive influencing parameter is the movement velocity of the vessels, as all wake components are more detectable the faster vessels move.
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Zilman, Gregory, and Touvia Miloh. "Kelvin and V-like Ship Wakes Affected by Surfactants." Journal of Ship Research 45, no. 02 (June 1, 2001): 150–63. http://dx.doi.org/10.5957/jsr.2001.45.2.150.
Повний текст джерелаАнотація:
Synthetic aperture radar (SAR) ship wake images in light wind and calm sea conditions frequently appear in the form of a bright V with a half-angle of 2 to 3 deg. Sophisticated and conflicting explanations of this phenomenon, based on the Bragg scattering mechanism, have been proposed. There is a belief that the narrow V-wake is not a part of the Kelvin wake. An alternative approach, which is not generally accepted, suggests that short divergent Kelvin waves may contribute to the V-wake imaging although these waves are mixed with unsteady surface waves generated by the ship-induced turbulence. Ship-generated divergent waves contaminated by surfactants and their radar backscattering cross section are studied. The hull of the ship is represented by a single layer of hydrodynamic singularities. The Green function of a point source moving below a free surface covered by surfactants is derived. A closed-form asymptotic solution for the far ship wave wake is obtained. It is used to calculate analytically the corresponding radar backscattering cross section. The radiative, viscous, and surfactant-induced decay of the V-wake brightness along the V-arms is discussed. The theoretical results are compared against available experimental data.
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Бимбереков, Павел, and Pavel Bimberekov. "GRAPHICAL ANALYSIS OF FREE-SURFACE WAVE FIELDS FROM MOVING SHIPS AND A PAIR OF CONSECUTIVE POSTS." Vestnik of Astrakhan State Technical University. Series: Marine engineering and technologies 2019, no. 4 (November 15, 2019): 7–22. http://dx.doi.org/10.24143/2073-1574-2019-4-7-22.
Повний текст джерелаАнотація:
The paper presents a comparison of the photographic material of the wave patterns resulted from the movement of a ship in situ and a model ship, as well as from two consecutive posts, their regularities being found through graphical processing. The possibility to find the fore imaginary source of Kelvin wave pattern forming the ship's wave system is given at a distance
of one wavelength before the top of the bow retaining wave. The equality of the length of trans-verse waves and divergent waves along the outer boundaries of the latter zone is fixed. It has been assumed that the intermediate waves generated between the main waves in the model ship and the posts are regular, imposition of wave patterns in a pair of consistently moving racks depending on the hit of the rear rack in the wave field of the first rack has been stated. Regularly occurring flows around moving posts are discussed. The bow and stern system of Kelvin waves in a ship wave sys-tem has been illustrated (the angle of the midpoint of diverging wave crests with the ship’s diamet-rical plane and the angle of diverging wave crests with the ship’s diametrical plane). The photo-graphs presented were taken in the experimental tank of Siberian State University of Water Transport (Novosibirsk State Academy of Water Transport) in 2006. A thin film naturally generat-ed on the water surface of the experimental tank and given a structure directed along the tank due to previous runs helped to visualize the distortion of the free water surface in better quality and to obtain clearly outlined contours in lighting.
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ROOS, P. C., and H. M. SCHUTTELAARS. "Horizontally viscous effects in a tidal basin: extending Taylor's problem." Journal of Fluid Mechanics 640 (October 27, 2009): 421–39. http://dx.doi.org/10.1017/s0022112009991327.
Повний текст джерелаАнотація:
The classical problem of Taylor (Proc. Lond. Math. Soc., vol. 20, 1921, pp. 148–181) of Kelvin wave reflection in a semi-enclosed rectangular basin of uniform depth is extended to account for horizontally viscous effects. To this end, we add horizontally viscous terms to the hydrodynamic model (linearized depth-averaged shallow-water equations on a rotating plane, including bottom friction) and introduce a no-slip condition at the closed boundaries.In a straight channel of infinite length, we obtain three types of wave solutions (normal modes). The first two wave types are viscous Kelvin and Poincaré modes. Compared to their inviscid counterparts, they display longitudinal boundary layers and a slight decrease in the characteristic length scales (wavelength or along-channel decay distance). For each viscous Poincaré mode, we additionally find a new mode with a nearly similar lateral structure. This third type, entirely due to viscous effects, represents evanescent waves with an along-channel decay distance bounded by the boundary-layer thickness.The solution to the viscous Taylor problem is then written as a superposition of these normal modes: an incoming Kelvin wave and a truncated sum of reflected modes. To satisfy no slip at the lateral boundary, we apply a Galerkin method. The solution displays boundary layers, the lateral one at the basin's closed end being created by the (new) modes of the third type. Amphidromic points, in the inviscid and frictionless case located on the centreline of the basin, are now found on a line making a small angle to the longitudinal direction. Using parameter values representative for the Southern Bight of the North Sea, we finally compare the modelled and observed tide propagation in this basin.
Дисертації з теми "Kelvin wave angle"
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Du, Peng. "Numerical modeling and prediction of ship maneuvering and hydrodynamics during inland waterway transport." Thesis, Compiègne, 2018. http://www.theses.fr/2018COMP2459.
Повний текст джерелаАнотація:
Dans cette thèse, l'hydrodynamique des navires lors du transport par voies navigables et des manœuvres sont étudiées à l'aide de la CFD (Computational Fluid Dynamics) basée sur OpenFoam. Des études de validation et de vérification sont réalisées pour la convergence de maillage, la convergence de pas de temps, la sensibilité aux modèles de turbulence et les techniques de maillage dynamique. Un solveur de mouvement 6DoF basé sur quaternion est mis en œuvre pour les prédictions d'assiette et d'enfoncement. Les effets environnementaux sur plusieurs bateaux de navigation intérieure (convoi 1, convoi 2, automoteur) sont étudiés à l'aide de modèles numériques validés. Trois aspects importants sont simulés: l'effet de confinement de la voie navigable, le croissement et l'interaction bateau-pile de pont. Les conditions d’essai couvrent un large éventail, y compris les différentes dimensions du canal, la profondeur de l’eau, le tirant d'eau et la vitesse. La résistance du navire, le type de vague, l’angle de Kelvin et l’élévation de la vague à des positions spécifiques sont étudiés en fonction de ces paramètres. La manœuvre des navires est étudiée à l’aide de tests de modèles captifs virtuels basés sur le modèle MMG (Mathematical Maneuvering Group). Un disque d'actionneur est implémenté pour remplacer l'hélice réelle. Les tests d'un modèle KVLCC2 sont effectués pour obtenir les coefficients hydrodynamiques de l'hélice, du gouvernail et de la coque du navire. En utilisant les coefficients obtenus, des simulations de manœuvre sont effectuées et validées. Ces études reproduisent des tests de navires réels et prouvent ainsi la validité de nos modèles numériques. En conséquence, le solveur numérique est prometteur dans les simulations d'hydrodynamique des navires et d'ingénierie marineIn this thesis, the ship hydrodynamics during inland waterway transport and ship maneuvering are investigated using CFD (Computational Fluid Dynamics) based onOpenFoam. Validation and verification studies are carried out for the mesh convergence, time step convergence, sensitivity to turbulence models and dynamic mesh techniques. A quaternion-based 6DoF motion solver is implemented for the trim and sinkage predictions. Environmental effects on several inland vessels (convoy 1, convoy 2, tanker) are studied using the validated numerical models. Three important aspects, the confinement effect of the waterway, head-on encounter and ship-bridge pile interaction are simulated. The testing conditions cover a wide range, including various channel dimensions, water depths, ship draughts and speeds. The ship resistance, wave pattern, Kelvin angle and wave elevation at specific positions are investigated as functions of these parameters. Ship maneuvering is investigated using virtual captive model tests based on the MMG (Mathematical Maneuvering Group) model. An actuator disk is implemented to replace the real propeller. Open water test, rudder force test, OTT (Oblique Towing Tank test) and CMT (Circular Motion Test) of a KVLCC2 model are carried out to obtain the hydrodynamic coefficients of the propeller, rudder and ship hull. Using the obtained coefficients, system-based maneuvering simulations are carried out and validated using the free running test data. These studies reproduce real ship tests and thus prove the validity of our numerical models. As a result, the numerical solver is promising in ship hydrodynamics and marine engineering simulations
Тези доповідей конференцій з теми "Kelvin wave angle"
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Li, Yan, and Simen Å. Ellingsen. "Effect of Anisotropic Shape on Ship Wakes in Presence of Shear Current of Uniform Vorticity." In ASME 2016 35th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/omae2016-54250.
Повний текст джерелаАнотація:
We analyze the interactions between a subsurface shear current of uniform vorticity and a moving surface disturbance of anisotropic shape which generates surface gravity waves. The problem extends previous analysis of ship waves in the presence of a shear current varying linearly with depth, now also accounting for the three dimensional shape of real ships, in order to study the interplay of aspect ratio and the shear current. Based on general solutions derived previously, we apply an elliptical Gaussian pressure disturbance at the surface moving at constant velocity as a model for a real “ship”. Wave contributions in the far field and expressions for the Mach angle (of maximum wave amplitude) based on asymptotic expressions for high Froude numbers, are derived thereafter. Through numerical calculations we present wave patterns, as well as Kelvin and Mach angles, at moderate Froude numbers under different shear strenghts and aspect ratios. Results show that the aspect ratio has negligible effect on the value of the critical shear vorticity and Kelvin angle, whereas a subtle interplay of aspect ratio and shear strenght is found to affect the Mach angle at moderate Froude numbers.
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Yang, Ray-Yeng, Ming-Chung Fang, and Igor V. Shugan. "Ship Wake Structure on the Finite Sea Depth in the Presence of Wind Waves." In ASME 2011 30th International Conference on Ocean, Offshore and Arctic Engineering. ASMEDC, 2011. http://dx.doi.org/10.1115/omae2011-49872.
Повний текст джерелаАнотація:
A kinematics model of the ship wake in the presence of surface waves, generated by wind is presented. It is found that the stationary wave structure behind the ship covered a wedge region with the 16.9° half an angle at the top of the wake and only divergent waves are present in a ship wake for co propagating wind waves. Wind waves field directed at some nonzero angle to the ship motion can cause essential asymmetry of the wake and compressing of its windward half. The extension of Whitham-Lighthill kinematics theory of ship wake for the intermediate sea depth is also presented. The ship wake structure essentially depends from the Froude (Fr) number based on the value of the sea depth and ship velocity. For Froude number less than unit both longitudinal and cross waves are presented in the wake region and Kelvin wake angle increased with Fr. For Fr>1 wake angle decreased with Froude number and finally only divergent waves directed almost normally to the ship track are presented in the very narrow ship wake.
3
Colistra, Joshua H., Mahesh V. Panchagnula, Alparslan O¨ztekin, Sudhakar Neti, and John Chen. "Interfacial Dynamics of Two Layer Couette Flow: Gravity Enhanced Kelvin-Helmholtz Instability." In ASME 2005 Fluids Engineering Division Summer Meeting. ASMEDC, 2005. http://dx.doi.org/10.1115/fedsm2005-77459.
Повний текст джерелаАнотація:
The Couette flow of two immiscible liquids is examined using flow visualization techniques. The flow dynamics are studied as a function of several independent parameters including gravity. The two fluids are initially separated by a sheet of aluminum sufficient in length to ensure that fully developed flow conditions are achieved for both fluids before they come in contact with each other. The experiments are performed for various flowrates of Canola Oil and Polyethylene Glycol (PEG) corresponding Reynolds numbers for Oil and PEG of 0 to 20 and 0.01 to 0.2 respectively. Photographic images of the flow field are recorded and analyzed with the aid of image analysis software to illustrate interfacial dynamics of the flow. A qualitative and quantitative analysis of the flow instability is performed for various inclinations of the test apparatus, including the extreme cases of upward vertical and downward vertical with the horizontal being the baseline test case. Neutral stability curves are identified for the range of variables studied in the experiments. The long wave instability is observed to be very periodic. At the onset of instability, the flow structure is three-dimensional and exhibits wave growth in the flow direction. The wave growth ultimately results in droplet pinch off from the crest of a folded wave. At a constant relative velocity, the wave length is at a minimum when the flow is oriented in the upward vertical direction, opposing gravity. For a given PEG flowrate, the critical Oil flowrate for the onset of interfacial instability decreases as the angle increases. These results indicate gravity enhanced Kelvin-Helmholtz interfacial instability even for low Reynolds numbers. Through a course of systematic variation of flow angles we have been able to separate the effects of inertia, gravity (buoyancy) and viscous shear forces on the wavelength of instability.
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Ohtake, Hiroyasu, and Yasuo Koizumi. "Study on Ex-Vessel Cooling of RPV: Model Analysis of Critical Heat Flux on Inclined Plate Facing Downward and Development to Hemispherical Surface." In 10th International Conference on Nuclear Engineering. ASMEDC, 2002. http://dx.doi.org/10.1115/icone10-22316.
Повний текст джерелаАнотація:
The cooling of the Ex-vessel in Light-Water-Reactors has been proposed to maintain reactor vessel integrity during severe accident. The critical heat flux — CHF — from the underside of down-facing convex surfaces, like hemispheres, is important to the assessment of the cooling. The authors examined CHFs on inclined plates under saturated boiling experimentally, focusing on the effect of the inclination angle on the CHF and characteristic length and velocity of coalesced bubbles near the heater at the CHF. In this study, the critical heat fluxes on the inclined plates in saturated boiling were investigated analytically by using the macrolayer model and the Kelvin-Helmholtz instability, based on our previous experimental report. Furthermore, the present model was developed for the CHF on a hemispheric surface. In the present model, the most dangerous wavelength and propagative velocity of the wave in the Kelvin-Helmholtz instability for ideal fluid with vapor flow of finite thickness and surface tension on liquid-vapor interface were calculated to determine the length and the velocity of the coalesced bubble on the heating surface at CHF. The time covered over the heater with the bubble was estimated as the calculated value with the length divided by the velocity. The predictions of the present CHF model by using the macrolayer model for CHF and the Kelvin-Helmholtz instability for the characteristic values of the coalesced bubble agree well with previous experimental data for CHF on inclined plates with 30 to 180 degree in orientation. Furthermore, the present model given as a function of the inclination angle relative to the horizontal downward plate was extended to CHF on a hemispheric surface. The CHFs obtained by the present model are in qualitative agreement with experimental data on hemispheres reported by some investigators.
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Jian, Liu, Duan Wenhua, Zhang Liangji, and Qiao Weiyang. "Effect of Suction Side Jet on the Shock Wave Boundary Layer Interaction in Transonic Turbine." In ASME Turbo Expo 2020: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/gt2020-16256.
Повний текст джерелаАнотація:
Abstract In this paper, the effect of round jet with inclination angle 135° upstream the throat on the suction surface on shock wave boundary-layer interaction was investigated in a transonic turbine cascade, and the vortical structures near the jet region were analyzed. Owing to locally high concave curvature on the pressure side profile, the double shock wave structure was obtained in the turbine passage near the pressure side trailing edge. The first incident shock does not induce the boundary layer separation. The second strong incident shock transmits from the trailing edge of the pressure side and reaches the suction side of the adjacent blade. Strong interaction between the suction side boundary layer and incident shock wave exists in this region, and the separation bubble appears in the no jet case. The complex shock wave system and corresponding flow characters are analyzed. Due to the complex vortical structures on the blade suction surface with suction side jet, the pressure distribution on the suction side changes, and the shock wave system in the transonic turbine passage is rearranged, thereby influencing the shock wave boundary layer interaction. The separation onset decays with the suction side jet, and it keeps move downstream with increasing jet velocity. Length of the separation bubble is significantly reduced with suction side jet. However, when the jet velocity is beyond a certain value, the effect of suction side jet will not improve. The complex vortical structures with suction side jet will reenergizing to the low momentum fluid within boundary layer, and the mean velocity profiles in the boundary layer near the shock wave boundary layer interaction religion with suction side jet are more solid than the no jet case, which infers stronger resistance to flow separation. Complicated vortical structures exist near jet region, the Kelvin–Helmholtz instabilities of the shear layer of the jet flow and its coherent structures dominate the unsteadiness of the suction surface. The incident shock wave enhances the pressure fluctuation in the SBLI region, whereas the effect concentrates only on the first harmonic of the K-H instability but not higher frequencies.