This paper explores the mechanisms underlying roughness induced transition (RIT) caused by discrete elements (DREs) using immersed boundary direct numerical simulations. We show via favorable comparison between RIT in Blasius layers and equivalent Couette flows that linear instability of layer profile does not play a significant role for DREs considered (k < 0.6δ*, where k is height DRE) k+ = uτk/ν dominant parameter (for given shape which strongly affects location. For suitable range...

Bubble trajectories in the presence of a decaying Lamb–Oseen vortex are calculated using modified Maxey–Riley equation. Some bubbles shown to get trapped within quasi-equilibrium states. All exit at time that is only function Galilei number and Reynolds number. The set initial bubble locations lead entrapment numerically determined show capturing potential single vortex. results provide insight into likelihood vortical structures turbulent flows.

Control and estimation of fluid systems is a challenging problem that requires approximating high-dimensional, nonlinear dynamics with computationally tractable models. A number techniques, such as proper orthogonal decomposition (POD) dynamic mode (DMD) have been developed to derive reduced-order In this letter, the selecting dynamically important modes control (DMDc) addressed. Similar sparsity-promoting DMD, method described in letter solves convex optimization order determine most modes....

Boundary-layer transition in the wake of a discrete roughness element results turbulent wedge that can adversely affect aerodynamic performance. Even when surfaces are designed for laminar flow, accumulates near leading edge cause premature and degrade One approach mitigating such is to place small spanwise-oriented shielding strips upstream or downstream potential elements accumulation sites. Shielding have been shown be effective at eliminating zero-pressure-gradient, flat-plate boundary...

The roughness-shielding concept involves reducing the receptivity of large-amplitude discrete roughness elements (DREs) by surrounding them with subcritical distributed roughness. present work studies effects upstream or downstream DREs using direct numerical simulations (DNS) and wind tunnel experiments suitable abstractions. elements, whose shapes are chosen to enable simple, matched studies, incorporated in DNS an immersed boundary method. detailed evolution different components vorticity...

Turbulent boundary layers are dominated by large-scale motions (LSMs) of streamwise momentum surplus and deficit that contribute significantly to the statistics flow. In particular, high-momentum LSMs residing in outer region layer have potential re-energize flow delay separation if brought closer wall. This work explores effect selectively manipulating a moderate Reynolds number turbulent for via well-resolved large-eddy simulations. Toward goal, model predictive control scheme is developed...

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTHeat Transfer to Pseudoplastic Fluids in an Agitated VesselS. Suryanarayanan, B. A. Mujawar, and M. Raja RaoCite this: Ind. Eng. Chem. Process Des. Dev. 1976, 15, 4, 564–569Publication Date (Print):October 1, 1976Publication History Published online1 May 2002Published inissue 1 October 1976https://pubs.acs.org/doi/10.1021/i260060a016https://doi.org/10.1021/i260060a016research-articleACS PublicationsRequest reuse permissionsArticle...

In this paper, a model predictive control algorithm for selectively steering material volumes in boundary layer is proposed. Using direct numerical simulations of laminar with Gaussian-distributed force field as the actuator, reduced-order linear wall-normal velocity dynamics on grid covering neighborhood actuator derived using sparsity-promoting dynamic mode decomposition control. The spatial evolution target volume probabilistically described by Gaussian mixture propagated Taylor's...

Although the free-shear or mixing layer has been a subject of extensive research over nearly century, there are certain fundamental issues that remain controversial. These include influence initial and downstream conditions on flow, effect velocity ratio across layer, nature any possible coupling between small scale dynamics large evolution thickness. In spirit temporal vortex-gas simulations Suryanarayanan et al. [“Free turbulent shear in point vortex gas as problem nonequilibrium...

This paper attempts to unravel any relations that may exist between turbulent shear flows and statistical mechanics through a detailed numerical investigation in the simplest case where both can be well defined. The flow considered for purpose is two-dimensional (2D) temporal free layer with velocity difference $\ensuremath{\Delta}U$ across it, statistically homogeneous streamwise direction ($x$) evolving from plane vortex sheet normal it ($y$) periodic-in-$x$ domain...

Accurate prediction of the mass flow rate through labyrinth seals is extremely important especially for rotodynamic analysis turbomachinery. The integral control volume based coefficient programs are no more accurate than accuracy leakage rate. A equation can be developed by comparing seal to a series orifices and cavities. An this type usually contains discharge carry-over coefficient. represents effectiveness each cavity dissipate kinetic energy entering has an effect upon value...

Abstract An alternate BGK type formulation of the Enskog equation has been recently proposed. It was shown that new model a valid H -theorem and correct thermal conductivity. We propose Lattice Boltzmann (LB) this Enskog-BGK model. The molecular nature is verified in case shear flow by comparing predicted normal stress behavior current with prediction dynamics simulations. extend for multiphase incorporating attractive part as Vlasov force. To validate formulation, results 3D simulations...

The accuracy of rotodynamic analysis any turbomachinery is dependent upon the seal leakage prediction. An expression for through a labyrinth can be developed by combining coefficient discharge under each tooth and carryover to account dissipation kinetic energy jet emerging from in subsequent cavity turbulence viscosity interaction. While most popularly used models consider carry-over only as function clearance pitch, it was established our earlier work that Reynolds number clearance/pitch...

A labyrinth seal leakage prediction equation can be developed by considering the as a series of orifices and cavities. CFD simulations are used to investigate discharge coefficient’s dependence each tooth upon geometry flow conditions for multi-toothed, teeth on stator, straight through seals with rectangular The coefficient first was found function width clearance ratio Reynolds number. It that coefficients downstream inlet is carry over coefficient. measure amount kinetic energy entering...

Discrete roughness elements in laminar boundary layers trigger breakdown to turbulence when the associated Reynolds number, Rekk, exceeds a critical value. Recent work by Suryanarayanan et al. (2017a) has demonstrated that for case of 45° - inclined rectangular at modest supercritical transition can be prevented placing second oppositely element wake upstream element. Extensive hotwire measurements downstream single and two-element configurations are made determine how addition suppresses...

Uredospores of Puccinia graminis var. tritici were incubated in phosphate buffer (pH 6.2) containing pelargonic acid-1-C 14 . After 3 hours 97.5% the tracer was assimilated. Fifty-five percent this released as C O 2 and 36.2% incorporated into spores. About one-half carbon-14 spores soluble ethanol water, whereas nearly a third ether extractable. The amino acid carbohydrate fractions contained about equal amounts together accounted for two-thirds radioactivity ethanol–water extract. organic...