87 results found
Chernyshenko SI, Zhang C, Butt H, et al., 2019, A large-scale filter for applications of QSQH theory of scale interactions in near-wall turbulence, FLUID DYNAMICS RESEARCH, Vol: 51, ISSN: 0169-5983
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
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
Ghebali S, Chernyshenko SI, Leschziner MA, Can large-scale oblique undulations on a solid wall reduce the turbulent drag?, Physics of Fluids, Vol: 29, Pages: 105102-105102
Direct numerical simulations of fully-developed turbulent channel flows withwavy walls are undertaken. The wavy walls, skewed with respect to the mean flowdirection, are introduced as a means of emulating a Spatial Stokes Layer (SSL)induced by in-plane wall motion. The transverse shear strain above the wavywall is shown to be similar to that of a SSL, thereby affecting the turbulentflow, and leading to a reduction in the turbulent skin-friction drag. Thepressure- and friction-drag levels are carefully quantified for various flowconfigurations, exhibiting a combined maximum overall-drag reduction of about0.5%. The friction-drag reduction is shown to behave approximatelyquadratically for small wave slopes and then linearly for higher slopes, whilstthe pressure-drag penalty increases quadratically. Unlike in the SSL case,there is a region of increased turbulence production over a portion of thewall, above the leeward side of the wave, thus giving rise to a local increasein dissipation. The transverse shear-strain layer is shown to be approximatelyReynolds-number independent when the wave geometry is scaled in wall units.
Ghebali S, Chernyshenko S, Leschziner M, 2017, Turbulent drag reduction by wavy wall, 10th International Symposium on Turbulence and Shear Flow Phenomena, TSFP 2017
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.
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.
Chernyshenko SI, Zhang C, Butt H, et al., 2017, Extrapolating statistics of turbulent flows to higher Re using quasi-steady theory of scale interaction in near-wall turbulence, 10th International Symposium on Turbulence and Shear Flow Phenomena, TSFP 2017
A new technique for extrapolating statistical characteristics of near-wall turbulence from medium to higher Re is outlined. Results for extrapolating the velocity two-point correlation from Reτ= 2003 to Reτ= 4179 and for the parameters of an optimized comb probe for detecting the large-scale velocity component required for applying the technique in practice are presented.
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
Zhang C, Chernyshenko SI, 2016, Quasisteady quasihomogeneous description of the scale interactions in near-wall turbulence, PHYSICAL REVIEW FLUIDS, Vol: 1, ISSN: 2469-990X
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
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
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
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
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, 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, 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
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
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
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.
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
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
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.
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
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
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
, 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.
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