88 results found
Blesbois O, Chernyshenko SI, 2011, Generalised optimal perturbation approach applied to drag reduction by wall oscillations in turbulent flows
© 2011 CURRAN-CONFERENCE. All rights reserved. Drag reduction by wall oscillations in turbulent flows has recently been shown to be a promising technique. The reduction of the near wall streaks amplitude is known to play a significant role in the drag reduction mechanism. To gain a better understanding of the effect of wall oscillations on the streaks, the Generalised Optimal Perturbation (GOP) approach, based on the linearised Navier-Stokes equation, is used. Resemblance between drag and certain quantities arising in the GOP context is observed. It is found that for harmonic wall oscillations the streaks have an approximately constant angle to the main flow direction, with a jump in sign twice in the period. The mechanism of this phenomenon is clarified. The results are in a reasonable agreement with direct numerical simulations.
Goulart PJ, Chernyshenko SI, 2010, Stability analysis of fluid flows using sum-of-squares, Pages: 2971-2976
In this paper we present a new method for assessing the stability of finite-dimensional approximations to the Navier-Stokes equation for fluid flows. Approximations to the Navier-Stokes equation typically take the form of a set of linear ODEs with an additional bilinear term that conserves the total energy of the system state. We suggest a structured method for generating Lyapunov functions using sum-of-squares optimization that exploits this energy conservation property. We provide a numerical example demonstrating the use of this technique to assess the stability of a model of a shear flow between infinite parallel plates. © 2010 AACC.
Sandoval M, Chernyshenko S, 2010, Extension of the Prandtl-Batchelor theorem to three-dimensional flows slowly varying in one direction, JOURNAL OF FLUID MECHANICS, Vol: 654, Pages: 351-361, ISSN: 0022-1120
Goulart PJ, Chernyshenko SI, 2010, Stability Analysis of Fluid Flows Using Sum-of-Squares, 2010 AMERICAN CONTROL CONFERENCE, Pages: 2971-2976, ISSN: 0743-1619
Nikitin NV, Chernyshenko SI, Wang HL, 2009, Turbulent flow and heat transfer in eccentric annulus, Pages: 601-604
Booker C, Zhang X, Chernyshenko S, 2009, Large-scale source term modeling of vortex generation, ISSN: 1048-5953
Methods of modeling vortex generation in computational fluid dynamics without mesh-ing the vortex generating device have been investigated. This is done by adding source terms to the governing equations to create vortices. Previous work in this area has focused on boundary layer control. This study looks at larger scale applications, such as using vortices for force enhancement. Two different approaches are tested. One is to model vortex generators directly, for which an existing method that replaces the force exerted on the fluid by a vortex generator with a source term is used. Also of this type, a simple im-mersed boundary method is used for comparison. The other approach uses source terms to create specified vortex velocity profiles. A method to add a continuous three-dimensional velocity is formulated and implemented in three ways; explicit calculation of the required forces from the Navier-Stokes equations, direct forcing (setting the velocity as boundary conditions), and penalty-type feedback forcing. After basic testing, all methods are applied in a practical engineering case using a commercial solver. Copyright © 2009 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.
Nikitin N, Wang H, Chernyshenko S, 2009, Turbulent flow and heat transfer in eccentric annulus, JOURNAL OF FLUID MECHANICS, Vol: 638, Pages: 95-116, ISSN: 0022-1120
Hetsch T, Savelsberg R, Chernyshenko SI, et al., 2009, Fast numerical evaluation of flow fields with vortex cells, EUROPEAN JOURNAL OF MECHANICS B-FLUIDS, Vol: 28, Pages: 660-669, ISSN: 0997-7546
Nikitin NV, Chernyshenko SI, Wang HL, 2009, Turbulent flow and heat transfer in eccentric annulus, 12th EUROMECH European Turbulence Conference, Publisher: SPRINGER-VERLAG BERLIN, Pages: 601-604, ISSN: 0930-8989
Chernyshenko SI, Bondarenko ME, 2008, Master-modes in 3D turbulent channel flow, arXiv:0809.2896 [physics.flu-dyn]
Turbulent flow fields can be expanded into a series in a set of basic functions. The terms of such series are often called modes. A master- (or determining) mode set is a subset of these modes, the time history of which uniquely determines the time history of the entire turbulent flow provided that this flow is developed. In the present work the existence of the master-mode-set is demonstrated numerically for turbulent channel flow. The minimal size of a master-mode set and the rate of the process of the recovery of the entire flow from the master-mode set history are estimated. The velocity field corresponding to the minimal master-mode set is found to be a good approximation for mean velocity in the entire flow field. Mean characteristics involving velocity derivatives deviate in a very close vicinity to the wall, while master-mode two-point correlations exhibit unrealistic oscillations. This can be improved by using a larger than minimal master-mode set. The near-wall streaks are found to be contained in the velocity field corresponding to the minimal master-mode set, and the same is true at least for the large-scale part of the longitudinal vorticity structure. A database containing the time history of a master-mode set is demonstrated to be an efficient tool for investigating rare events in turbulent flows. In particular, a travelling-wave-like object was identified on the basis of the analysis of the database. Two master-mode-set databases of the time history of a turbulent channel flow were made available online. The services provided include the facility for the code uploaded by a user to be run on the server with an access to the data.
Chernyshenko SI, Constantin P, Robinson JC, et al., 2007, A posteriori regularity of the three-dimensional Navier-Stokes equations from numerical computations, JOURNAL OF MATHEMATICAL PHYSICS, Vol: 48, ISSN: 0022-2488
Chernyshenko SI, Bondarenko ME, 2007, Master-mode set for 3D turbulent channel flow, 11th EUROMECH European Turbulence Conference, Publisher: SPRINGER-VERLAG BERLIN, Pages: 188-190, ISSN: 0930-8989
Chernyshenko SI, Di Cicca GM, Iollo A, et al., 2006, Analysis of Data on the Relation between Eddies and Streaky Structures in Turbulent Flows Using the Placebo Method, FLUID DYNAMICS, Vol: 41, Pages: 772-783, ISSN: 0015-4628
Chernyshenko SI, Baig MF, 2005, The mechanism of streak formation in near-wall turbulence, JOURNAL OF FLUID MECHANICS, Vol: 544, Pages: 99-131, ISSN: 0022-1120
Bondarenko ME, Chernyshenko SI, 2005, Master-modes of the 3D turbulent channel flow, American Physical Society, 58th Annual Meeting of the Division of Fluid Dynamics
Using Chebychev-Fourier representation of Direct Numerical Simulation solution we determine the so-called master modes, that is those modes which contain all essential information about the flow. The method used by E. Olson and E.S. Titi for 2D case is applied for 3D turbulent channel flow (i.e. Determining modes for continuous data assimilation in 2D turbulence, Journal of Statistical Physics, 113 (2003), 799-840). Initial simulation performed with 32786 Chebychev-Fourier modes using a spatial domain with streamwise and spanwise periods of 1.6 π revealed that the number of master-modes for Reτ=85 is N≤650. Number of master-modes is not the same as, but may be related to, the fractal dimension of the attractor. For the comparison, L. Keefe, J. Kim and P. Moin estimated the fractal dimension as Dλ=780 for Reτ=80. (i.e. The dimension of attractors underlying periodic turbulent Poiseuille flow, J. Fluid Mech (1992), vol. 242, pp.1-29). Results for higher Reτ will be obtained, analysed and reported at the conference. In particular we are interested in what organised structures will appear in the master modes
Chernyshenko SI, Baig MF, 2005, Streaks and vortices in near-wall turbulence, Workshop on New Developments and Application in Rapid Fluid Flows, Publisher: ROYAL SOCIETY, Pages: 1097-1107, ISSN: 1364-503X
Zannetti L, Chernyshenko SI, 2005, Vortex pair and Chaplygin cusps, EUROPEAN JOURNAL OF MECHANICS B-FLUIDS, Vol: 24, Pages: 328-337, ISSN: 0997-7546
Bouferrouk A, Chernyshenko SI, 2005, Tikhonov regularisation in discrete vortex methods, COMPUTERS & FLUIDS, Vol: 34, Pages: 275-281, ISSN: 0045-7930
Baig MF, Chernyshenko SI, 2004, Regeneration mechanism of streaks in near-wall quasi-2D turbulence, EUROPEAN JOURNAL OF MECHANICS B-FLUIDS, Vol: 23, Pages: 727-736, ISSN: 0997-7546
Chernyshenko SI, Privalov AV, 2004, Internal degrees of freedom of an actuator disk model, JOURNAL OF PROPULSION AND POWER, Vol: 20, Pages: 155-163, ISSN: 0748-4658
Chernyshenko SI, Galletti B, Lo AI, et al., 2003, Trapped vortices and a favourable pressure gradient, JOURNAL OF FLUID MECHANICS, Vol: 482, Pages: 235-255, ISSN: 0022-1120
Buldakov EV, Chernyshenko SI, Ruban AI, 2000, On the uniqueness of steady flow past a rotating cylinder with suction, JOURNAL OF FLUID MECHANICS, Vol: 411, Pages: 213-232, ISSN: 0022-1120
Chernyshenko SI, 1999, Non-linear development of rotating stall in an axial flow compressor at near-critical flow rate, Prikladnaya Matematika i Mekhanika, Vol: 63, Pages: 457-466, ISSN: 0032-8235
Chernyshenko SI, 1999, Non-linear development of rotating stall in an axial compressor at a near-critical flow rate, PMM JOURNAL OF APPLIED MATHEMATICS AND MECHANICS, Vol: 63, Pages: 439-447, ISSN: 0021-8928
Teverovskij MA, Chernyshenko SI, 1998, Vortex flow in outlet channel of axial-flow compressor under conditions of rotary separation, Izvestiya Akademii Nauk. Mekhanika Zhidkosti I Gaza, Pages: 58-71, ISSN: 0568-5281
Bunyakin AV, Chernyshenko SI, Stepanov GY, 1998, High-Reynolds-number Batchelor-model asymptotics of a flow past an aerofoil with a vortex trapped in a cavity, JOURNAL OF FLUID MECHANICS, Vol: 358, Pages: 283-297, ISSN: 0022-1120
Teverovskii MA, Chernyshenko SI, 1998, Vortex flow in the outlet duct of an axial compressor in the rotating stall regime, Fluid Dynamics, Vol: 33, Pages: 683-693, ISSN: 0015-4628
An ideal incompressible fluid flow in the right half-plane periodic in the transverse direction is considered. This flow models that in the outlet duct of an axial compressor in the rotating stall regime. It is a feature of the problem that in the inlet cross-section two velocity components are prescribed while the vorticity distribution is unknown. An explicit solution is found in the form of a series in a small parameter characterizing the deviation of the velocity from a constant value. Numerical results are obtained.
Chernyshenko SI, 1998, Asymptotic theory of global separation, Applied Mechanics Reviews, Vol: 51, Pages: 523-536, ISSN: 0003-6900
This article aims to review the recent achievements and the state of the art in the high Reynolds number asymptotic theory of steady separated flow past bluff bodies for a general reader specializing in fluid dynamics who is not necessarily familiar with modem asymptotic techniques. A short historical overview is given. The ideas of the mathematical methods used are briefly outlined. Then the general structure of the solution for a plane flow past a bluffbody is described. The physical mechanisms of such a flow are discussed, and quantitative results are given and compared with numerical calculations. Existing extensions of the theory and the latest results for axisymmetric flows are described. In conclusion, the relationship between asymptotic theory and real turbulent flows is discussed. This review article contains 76 references. © 1998 American Society of Mechanical Engineers.
Nikitin NV, Chernyshenko SI, 1997, On the nature of organized structures in turbulent wall flows, Izvestiya Akademii Nauk. Mekhanika Zhidkosti I Gaza, Pages: 24-31, ISSN: 0568-5281
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