83 results found
Chernyshenko S, 2017, Relationship between the methods of bounding time averages
The problem of finding bounds of time-averaged characteristics of dynamicalsystems, such as for example the bound on the mean energy dissipation rate in aturbulent flow governed by incompressible Navier-Stokes equations, isconsidered. It is shown that both the well-known background flow method ofDoering and Constantin and the direct method proposed by Seis in 2015correspond to the same quadratic storage functional in the framework of theindefinite storage functional method. In particular, a background flow can befound corresponding to the linear functional used in the direct method and viceversa. It is shown that any bound obtained with the background flow method canalso be obtained by the direct method. The reverse is true subject to anadditional constraint. The relative advantages of the three methods arediscussed.
Ghebali S, Chernyshenko S, Leschziner M, 2017, Turbulent drag reduction by wavy wall
Copyright © 2016 Zakon Group LLC. Fully-developed turbulent flow in channels with oblique wavy walls is analysed, from a drag-reduction perspective, by means of Direct Numerical Simulations (DNS). The wavy geometry is chosen to emulate the shear strain produced by a Spatial Stokes Layer (SSL) generated by oscillatory wall motion. As the cost of performing a parametric optimisation is prohibitive, an alternate solution is presented, based on a linear model of a perturbed plane-channel flow, using a turbulent viscosity. Flow properties and levels of drag reduction or increase are reported for various configurations.
Ghebali S, Chernyshenko SI, Leschziner MA, 2017, Can large-scale oblique undulations on a solid wall reduce the turbulent drag?, PHYSICS OF FLUIDS, Vol: 29, ISSN: 1070-6631
Huang D, Jin B, Lasagna D, et al., 2017, Expensive Control of Long-Time Averages Using Sum of Squares and Its Application to A Laminar Wake Flow, IEEE TRANSACTIONS ON CONTROL SYSTEMS TECHNOLOGY, Vol: 25, Pages: 2073-2086, ISSN: 1063-6536
Fantuzzi G, Goluskin D, Huang D, et al., 2016, Bounds for Deterministic and Stochastic Dynamical Systems using Sum-of-Squares Optimization, SIAM JOURNAL ON APPLIED DYNAMICAL SYSTEMS, Vol: 15, Pages: 1962-1988, ISSN: 1536-0040
Huang D, Chernyshenko S, 2016, LONG-TIME AVERAGE COST CONTROL OF POLYNOMIAL SYSTEMS: A SUM-OF-SQUARES-BASED SMALL-FEEDBACK APPROACH, 8th ASME Annual Dynamic Systems and Control Conference (DSCC 2015), Publisher: AMER SOC MECHANICAL ENGINEERS
Lasagna D, Huang D, Tutty OR, et al., 2016, Sum-of-squares approach to feedback control of laminar wake flows, JOURNAL OF FLUID MECHANICS, Vol: 809, Pages: 628-663, ISSN: 0022-1120
Lasagna D, Huang D, Tutty OR, et al., 2016, Controlling Fluid Flows with Positive Polynomials, 35th Chinese Control Conference (CCC), Publisher: IEEE, Pages: 1301-1306, ISSN: 2161-2927
Lasagna D, Tutty OR, Chernyshenko S, 2016, Flow regimes in a simplified Taylor-Couette-type flow model, EUROPEAN JOURNAL OF MECHANICS B-FLUIDS, Vol: 57, Pages: 176-191, ISSN: 0997-7546
Zhang C, Chernyshenko SI, 2016, Quasisteady quasihomogeneous description of the scale interactions in near-wall turbulence, PHYSICAL REVIEW FLUIDS, Vol: 1, ISSN: 2469-990X
Huang D, Chernyshenko S, 2015, Low-order State-feedback Controller Design for Long-time Average Cost Control of Fluid Flow Systems: A Sum-of-squares Approach, 34th Chinese Control Conference (CCC), Publisher: IEEE, Pages: 2479-2484, ISSN: 2161-2927
Huang D, Chernyshenko S, 2015, Long-time Average Cost Control of Stochastic Systems Using Sum of Squares of Polynomials, 34th Chinese Control Conference (CCC), Publisher: IEEE, Pages: 2344-2349, ISSN: 2161-2927
Huang D, Chernyshenko S, Goulart P, et al., 2015, Sum-of-squares of polynomials approach to nonlinear stability of fluid flows: an example of application, PROCEEDINGS OF THE ROYAL SOCIETY A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES, Vol: 471, ISSN: 1364-5021
Huang D, Chernyshenko S, Lasagna D, et al., 2015, Long-time Average Cost Control of Polynomial Systems: A Sum of Squares Approach, European Control Conference (ECC), Publisher: IEEE, Pages: 3244-3249
Chernyshenko SI, Goulart P, Huang D, et al., 2014, Polynomial sum of squares in fluid dynamics: a review with a look ahead, PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES, Vol: 372, ISSN: 1364-503X
Blesbois O, Chernyshenko SI, Touber E, et al., 2013, Pattern prediction by linear analysis of turbulent flow with drag reduction by wall oscillation, JOURNAL OF FLUID MECHANICS, Vol: 724, Pages: 607-641, ISSN: 0022-1120
Chernyshenko S, 2013, Drag reduction by a solid wall emulating spanwise oscillations. Part 1
A new idea for turbulent skin-friction reduction is proposed, wherein theshape of the solid wall is designed to create the spanwise pressure gradientacting similarly to the well-known method of drag reduction by in-planespanwise wall motion. Estimates based on the assumption of similarity with dragreduction effect of in-plane wall motion suggest that drag reduction of about2.4% can be achieved in the flow past a wavy wall, with the crests forming anangle of about 38 degrees with the main flow direction, and the wave period inthe main flow direction equal to about 1500 wall units. The required height ofthe wall waves have to be adjusted to achieve the same intensity of thespanwise motion as that created by an in-plane moving wall of the samewavelength and with peak wall velocity equal to 2 wall units. Further researchis being conducted in order to determine this height. Suggestions are made forfurther research on confirming the feasibility of the proposed method and onoptimising the wall shape.
Chernyshenko S, Huang D, Goulart P, et al., 2013, Nonlinear Stability Analysis of Fluid Flow using Sum of Squares of Polynomials, 11th International Conference of Numerical Analysis and Applied Mathematics (ICNAAM), Publisher: AMER INST PHYSICS, Pages: 265-268, ISSN: 0094-243X
Mathis R, Marusic I, Chernyshenko SI, et al., 2013, Estimating wall-shear-stress fluctuations given an outer region input, JOURNAL OF FLUID MECHANICS, Vol: 715, Pages: 163-180, ISSN: 0022-1120
Vodop'yanov IS, Nikitin NV, Chernyshenko SI, 2013, Turbulent drag reduction by spanwise oscillations of a ribbed surface, FLUID DYNAMICS, Vol: 48, Pages: 461-470, ISSN: 0015-4628
Chernyshenko SI, Marusic I, Mathis R, 2012, Quasi-steady description of modulation effects in wall turbulence
A theoretical description of the phenomenon of modulation of near-wallturbulence by large scale structures is investigated. The description given issimple in that the effect of large-scale structures is limited to aquasi-steady response of the near-wall turbulence to slow large-scalefluctuations of the skin friction. The most natural and compact form ofexpressing this mechanism is given by the usual Reynolds-number-independentrepresentation of the total skin friction and velocity, scaled in wallvariables, where the mean quantities are replaced by large-scalelow-pass-filtered fluctuating components. The theory is rewritten in terms offuctuations via a universal mean velocity and random mean square fluctuationvelocity profiles of the small-scales and then linearised assuming that thelarge-scale fluctuations are small as compared to the mean components. Thisallows us to express the superposition and modulation coefficients of theempirical predictive models of the skin friction and streamwise fluctuatingvelocity given respectively by Marusic et al. (13th Eur. Turb. Conf., 2011) andMathis et al. (J. Fluid Mech. 2011, vol. 681, pp. 537-566). It is found thatthe theoretical quantities agree well with experimentally determinedcoefficients.
Duque-Daza CA, Baig MF, Lockerby DA, et al., 2012, Modelling turbulent skin-friction control using linearized Navier-Stokes equations, JOURNAL OF FLUID MECHANICS, Vol: 702, Pages: 403-414, ISSN: 0022-1120
Goulart PJ, Chernyshenko S, 2012, Global stability analysis of fluid flows using sum-of-squares, PHYSICA D-NONLINEAR PHENOMENA, Vol: 241, Pages: 692-704, ISSN: 0167-2789
Booker CD, Zhang X, Chernyshenko SI, 2011, Large-Scale Vortex Generation Modeling, JOURNAL OF FLUIDS ENGINEERING-TRANSACTIONS OF THE ASME, Vol: 133, ISSN: 0098-2202
Daque CA, Baig MF, Lockerby DA, et al., 2011, Modelling turbulent skin-friction control using linearised Navier-Stokes equations, 13th European Turbulence Conference (ETC), Publisher: IOP PUBLISHING LTD, ISSN: 1742-6588
Wang HL, Nikitin NV, Chernyshenko SI, 2011, Identification of a Laminar-Turbulent Interface in Partially Turbulent Flow, FLUID DYNAMICS, Vol: 46, Pages: 911-916, ISSN: 0015-4628
Goulart PJ, Chernyshenko SI, 2010, Stability Analysis of Fluid Flows Using Sum-of-Squares, 2010 AMERICAN CONTROL CONFERENCE, Pages: 2971-2976, ISSN: 0743-1619
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
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.
This data is extracted from the Web of Science and reproduced under a licence from Thomson Reuters. You may not copy or re-distribute this data in whole or in part without the written consent of the Science business of Thomson Reuters.