Calculation of Convective Heat Transfer in Recirculating Turbulent Flow Using Various Near-Wall Turbulence Models

Abstract

The turbulentflow obout a two-dimensional blunt rectangular section is used os o test case to examine the performonce of seven neorwoll turbulence models. The Jint two models ore one-equotion low Reynolds number (Re) models requiring o fine grid neorwoll treatment. The other neorwoll turbulence models considered ore based on wollfunctions t h bridge with a single cell the thermally importnnt neorwoll region. Standard woll functions bosed on the local equilibrium assumption, woll functions using o two-and three-layer oppmach to evoluote locol variations of turbulence quadies in the k equation, ond extension of the two-ond three-layer treatments to the c eqvation o n considered. m e numerieol predictions ore obtoined using o variant of the k+ model incorpomtr'ng o curvoture correction. The governing eguoiions ore discretized using oJinite-volume formulolion employing the bounded-skew hybrid differencing scheme. The solutions ore obtained using a two-pass procedure, devised to allow for the correct use of the woll functions. CompuWns ore pegormed for Re in the mnge 20,000-75.000. The various neorwoll models ore assessed by compPMng resulting Nusselt number distributions and selected fluid dynamic results with ov&le experimenlol o h . A three-layer model of the woll region, applied to the k ond e equafions, gives good ognement with the data; the standard w d function treatment is not sotisfnclry ot oll for this flow.

Interaction between Crosswind and Aviation-Fuel Fire Engulfing a Full-Scale Composite-Type Aircraft: A Numerical Study

“…Flame radiation flux, , is computed from a discrete representation of the radiative intensity Equation (11). The Couette flow is assumed to prevail near the wall surface, and the convective heat feedback is calculated from a wall function [28] far away from the wall for viscous effects to be negligible, that is at y + ≥ 11.…”

“…Here, Cμ and E are the constants in the logarithmic law of the wall, κ is the von Karman constant, Pr the Prandtl number, Cp the gas specific heat and P an empirical function defined by Djilali [28].…”

Mathematical Modelling of Pool Fire Burning Rates in a Full- Scale Ventilated Tunnel

“…A wall-damping is treated by using a wall function for convective heat feedback due to the coarse meshes used here. The Couette flow is assumed to prevail near the wall surface, and the convective heat feedback is calculated from a wall function [21] far away from the wall for viscous effects to be negligible, that is,…”

“…Here  C and E (=9) are the constants in logarithmic law of the wall,  (=0.41) is the von Karman constant and P an empirical function [21] determined from the ratio between the laminar Prandtl number (Pr=0.7) and turbulent one (Pr t =0.5). Based on a quasi-steady assumption, the liquid pool vaporization rate, m " s  , can be derived from the combination of the species and energy equations [22], and expressed as follows :…”

A versatile software tool for the numerical simulation of fluid flow and heat transfer in simple geometries

“…where r (kg/m 3 ) is the fluid density, u (m/s) and w (m/s) are the velocity components along the horizontal axis x (m) and the along the vertical axis z (m), t (s) represents time, G is the diffusion coefficient of f and S f is the generation rate of f per unit volume. The different terms of the previous equation may be interpreted as: A-transient term; B-advection term; C-diffusion term; D-source term.…”