Particle Concentration Variation for Inflow Profiles in High Reynolds Number Turbulent Boundary Layer

2020 ◽  
Author(s):  
Mustafa M. Rahman ◽  
Ravi Samtaney
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Turbulent Flows ◽  
Particle Concentration ◽  
Solid Particles ◽  
Scale Model ◽  
Normal Velocity ◽  
Boundary Layer Flows ◽  
Ground Field ◽  
High Reynolds

Abstract Large-eddy simulations (LES) of incompressible turbulent boundary-layer flows can simulate a fundamental unsteady turbulent flow, including time-variant streamwise and wall-normal velocity as well as the near-wall locations of significant turbulence intensities. A typical illustration of turbulent flows with such high Reynolds numbers can be roughly approximated to atmospheric boundary-layer flows. To bypass the demanding mesh criteria of near-ground field and direct numerical simulations, we adopt a virtual-wall model with a stretched-vortex subgrid-scale model. We simulate the dynamics of solid particles in this wall-modeled LES approach toward incompressible flow. The particles considered are both charged and uncharged, and have a fixed concentration profile with no fluctuations at the inflow. An extended streamwise simulation domain is implemented as an alternative to rerunning the simulation with a turbulent inflow profile from the simulation of the previous downstream profile. By extending the streamwise domain, the fluctuation dynamics of the particles reach a steady state far downstream from the inflow. The streamwise and altitude variation of the particle parameters are compared for various particle-concentration inflow profiles. Furthermore, an estimate of the streamwise variation of parameters is also observed. This study is the first step towards enhancing our understanding of the particle dynamics in turbulent flows.

The effects of successive distortions on a turbulent boundary layer in a supersonic flow

1997 ◽  
Vol 351 ◽  
pp. 253-288 ◽  
Author(s):  
DOUGLAS R. SMITH ◽  
ALEXANDER J. SMITS
Keyword(s):  
Boundary Layer ◽  
Supersonic Flow ◽  
Turbulent Boundary Layer ◽  
Flow Direction ◽  
Initial Boundary ◽  
Turbulent Shear ◽  
Boundary Layer Flows ◽  
Turbulent Shear Stress ◽  
Small Change ◽  
High Reynolds

Experiments were conducted to investigate the response of a high-Reynolds-number turbulent boundary layer in a supersonic flow to the perturbation presented by a forward-facing ramp. Two ramps were used: one with sharp corners, the other with rounded corners having radii of curvature equal to 15 initial boundary layer thicknesses. The flow was turned through 20° in each of the compressions and expansions. Hence, there was no net change in the flow direction over the ramps and only a small change in free-stream conditions due to the entropy increase across relatively weak shocks. The two experiments gave similar results. In the middle of the relaxing boundary layer, the streamwise Reynolds stress undershot the undisturbed levels and exhibited a response similar to that observed in subsonic boundary layer flows recovering from an impulse of streamline curvature (Smits, Young & Bradshaw 1979b). The turbulent shear stress vanished throughout most of the boundary layer, and an overall destruction of the turbulence production mechanisms was apparent as the boundary layer exhibited a slow recovery.

Constant Pressure Laminar, Transitional and Turbulent Flows—An Approximate Unified Treatment

2002 ◽  
Vol 124 (3) ◽  
pp. 806-808
Author(s):  
J. Dey
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Turbulent Flows ◽  
Constant Pressure ◽  
Transitional Flow ◽  
Two Dimensional ◽  
Boundary Layer Flows

A nondimensional number that is constant in two-dimensional, incompressible and constant pressure laminar and fully turbulent boundary layer flows has been proposed. An extension of this to constant pressure transitional flow is discussed.

scholarly journals On the different contributions of coherent structures to the spectra of a turbulent round jet and a turbulent boundary layer

2001 ◽  
Vol 448 ◽  
pp. 367-385 ◽  
Author(s):  
T. B. NICKELS ◽  
IVAN MARUSIC
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Turbulent Flows ◽  
Coherent Structures ◽  
Isotropic Turbulence ◽  
Structural Models ◽  
Spectral Measurements ◽  
Round Jet ◽  
Good Account ◽  
Single Size

This paper examines and compares spectral measurements from a turbulent round jet and a turbulent boundary layer. The conjecture that is examined is that both flows consist of coherent structures immersed in a background of isotropic turbulence. In the case of the jet, a single size of coherent structure is considered, whereas in the boundary layer there are a range of sizes of geometrically similar structures. The conjecture is examined by comparing experimental measurements of spectra for the two flows with the spectra calculated using models based on simple vortex structures. The universality of the small scales is considered by comparing high-wavenumber experimental spectra. It is shown that these simple structural models give a good account of the turbulent flows.

Measurements in a Turbulent Boundary Layer Over a d-Type Surface Roughness

1975 ◽  
Vol 42 (3) ◽  
pp. 591-597 ◽  
Author(s):  
D. H. Wood ◽  
R. A. Antonia
Keyword(s):  
Boundary Layer ◽  
Surface Roughness ◽  
Turbulent Boundary Layer ◽  
Turbulent Energy ◽  
Shear Stresses ◽  
Normal Velocity ◽  
Mean Velocity ◽  
Outer Flow ◽  
Intensity Measurements ◽  
Normal And Shear Stresses

Mean velocity and turbulence intensity measurements have been made in a fully developed turbulent boundary layer over a d-type surface roughness. This roughness is characterised by regular two-dimensional elements of square cross section placed one element width apart, with the cavity flow between elements being essentially isolated from the outer flow. The measurements show that this boundary layer closely satisfies the requirement of exact self-preservation. Distribution across the layer of Reynolds normal and shear stresses are closely similar to those found over a smooth surface except for the region immediately above the grooves. This similarity extends to distributions of third and fourth-order moments of longitudinal and normal velocity fluctuations and also to the distribution of turbulent energy dissipation. The present results are compared with those obtained for a k-type or sand grained roughness.

Free-stream coherent structures in parallel boundary-layer flows

2014 ◽  
Vol 752 ◽  
pp. 602-625 ◽  
Author(s):  
Kengo Deguchi ◽  
Philip Hall
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
Coherent Structures ◽  
Free Stream ◽  
Stokes Equations ◽  
Navier Stokes ◽  
Homotopy Continuation ◽  
Boundary Layer Flows ◽  
Navier Stokes Equations ◽  
High Reynolds

AbstractOur concern in this paper is with high-Reynolds-number nonlinear equilibrium solutions of the Navier–Stokes equations for boundary-layer flows. Here we consider the asymptotic suction boundary layer (ASBL) which we take as a prototype parallel boundary layer. Solutions of the equations of motion are obtained using a homotopy continuation from two known types of solutions for plane Couette flow. At high Reynolds numbers, it is shown that the first type of solution takes the form of a vortex–wave interaction (VWI) state, see Hall & Smith (J. Fluid Mech., vol. 227, 1991, pp. 641–666), and is located in the main part of the boundary layer. On the other hand, here the second type is found to support an equilibrium solution of the unit-Reynolds-number Navier–Stokes equations in a layer located a distance of $\def \xmlpi #1{}\def \mathsfbi #1{\boldsymbol {\mathsf {#1}}}\let \le =\leqslant \let \leq =\leqslant \let \ge =\geqslant \let \geq =\geqslant \def \Pr {\mathit {Pr}}\def \Fr {\mathit {Fr}}\def \Rey {\mathit {Re}}O(\ln \mathit{Re})$ from the wall. Here $\mathit{Re}$ is the Reynolds number based on the free-stream speed and the unperturbed boundary-layer thickness. The streaky field produced by the interaction grows exponentially below the layer and takes its maximum size within the unperturbed boundary layer. The results suggest the possibility of two distinct types of streaky coherent structures existing, possibly simultaneously, in disturbed boundary layers.

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