Study of a Turbulent Dual Jet Consisting of a Wall Jet and an Offset Jet

The study of a two-dimensional, steady, incompressible, turbulent flow of a dual jet consisting of a wall jet and an offset jet has been simulated numerically. The standard high Reynolds number two-equation k-ɛ model is used as the turbulence model. The Reynolds number is considered as 20000 for all the computations because the flow becomes fully turbulent. The merge point and the combined point have been obtained and compared with other results. The central streamline has been plotted and observed to follow an arc of a circle. The momentum flux has been computed along the axial length for the wall jet, offset jet and the dual jet and compared. A similarity profile has been obtained in the downstream direction. A detailed discussion has been provided on the pressure field, Reynolds stress, kinetic energy and its dissipation rate. The jet growth rate in terms of half-width, the decay of maximum velocity and the jet width are presented

Download Full-text

A Modified Form of the k-ε Model for Predicting Wall Turbulence

Journal of Fluids Engineering ◽

10.1115/1.3240815 ◽

1981 ◽

Vol 103 (3) ◽

pp. 456-460 ◽

Cited By ~ 580

Author(s):

C. K. G. Lam ◽

K. Bremhorst

Keyword(s):

Reynolds Number ◽

Pipe Flow ◽

Dissipation Rate ◽

High Reynolds Number ◽

Present Form ◽

Wall Turbulence ◽

Wall Region ◽

Wall Function ◽

High Reynolds ◽

Number Form

The high Reynolds number form of the k-ε model is extended and tested by application to fully developed pipe flow. It is established that the model is valid throughout the fully turbulent, semilaminar and laminar regions of the flow. Unlike many previously proposed forms of the k-ε model, the present form does not have to be used in conjunction with empirical wall function formulas and does not include additional terms in the k and ε equations. Comparison between predicted and measured dissipation rate in the important wall region is also possible.

Download Full-text

Pressure Field of High Reynolds Number Turbulent Pulsed Jets

32nd AIAA Applied Aerodynamics Conference ◽

10.2514/6.2014-3099 ◽

2014 ◽

Author(s):

Jean Calzada ◽

Issac Choutapalli

Keyword(s):

Reynolds Number ◽

High Reynolds Number ◽

Pressure Field ◽

Pulsed Jets ◽

High Reynolds

Download Full-text

Computational Study of Heat Transfer in a Conjugate Turbulent Wall Jet Flow at High Reynolds Number

Journal of Heat Transfer ◽

10.1115/1.2908429 ◽

2008 ◽

Vol 130 (7) ◽

Cited By ~ 6

Author(s):

E. Vishnuvardhanarao ◽

Manab Kumar Das

Keyword(s):

Heat Transfer ◽

Reynolds Number ◽

Nusselt Number ◽

High Reynolds Number ◽

Computational Study ◽

Local Heat ◽

Interface Temperature ◽

Slab Thickness ◽

Wall Jet ◽

High Reynolds

In the present case, the conjugate heat transfer involving the cooling of a heated slab by a turbulent plane wall jet has been numerically solved. The bottom of the solid slab is maintained at a hot uniform temperature, whereas the wall jet temperature, is equal to the ambient temperature. The Reynolds number considered is 15,000 because it has already been experimentally found and reported that the flow becomes fully turbulent and is independent of the Reynolds number. The high Reynolds number two-equation model (κ‐ϵ) has been used for the turbulence modeling. The parameters chosen for the study are the conductivity ratio of the solid-fluid (K), the solid slab thickness (S), and the Prandtl number (Pr). The ranges of parameters are K=1–1000, S=1–10, and Pr=0.01–100. Results for the solid-fluid interface temperature, local Nusselt number, local heat flux, average Nusselt number, and average heat transfer are presented and discussed.

Download Full-text

The decay of turbulence generated by a class of multiscale grids

Journal of Fluid Mechanics ◽

10.1017/jfm.2011.353 ◽

2011 ◽

Vol 687 ◽

pp. 300-340 ◽

Cited By ~ 92

Author(s):

P. C. Valente ◽

J. C. Vassilicos

Keyword(s):

Reynolds Number ◽

Dissipation Rate ◽

High Reynolds Number ◽

Transverse Energy ◽

Mean Flow ◽

Integral Scale ◽

Square Grid ◽

Turbulence Decay ◽

Classical Behaviour ◽

High Reynolds

AbstractA new experimental investigation of decaying turbulence generated by a low-blockage space-filling fractal square grid is presented. We find agreement with previous works by Seoud & Vassilicos (Phys. Fluids, vol. 19, 2007, 105108) and Mazellier & Vassilicos (Phys. Fluids, vol. 22, 2010, 075101) but also extend the length of the assessed decay region and consolidate the results by repeating the experiments with different probes of increased spatial resolution. It is confirmed that this moderately high Reynolds number${\mathit{Re}}_{\lambda } $turbulence (up to${\mathit{Re}}_{\lambda } \simeq 350$here) does not follow the classical high Reynolds number scaling of the dissipation rate$\varepsilon \ensuremath{\sim} {u{}^{\ensuremath{\prime} } }^{3} / L$and does not obey the equivalent proportionality between the Taylor-based Reynolds number${\mathit{Re}}_{\lambda } $and the ratio of integral scale$L$to the Taylor microscale$\lambda $. Instead we observe an approximate proportionality between$L$and$\lambda $during decay. This non-classical behaviour is investigated by studying how the energy spectra evolve during decay and examining how well they can be described by self-preserving single-length-scale forms. A detailed study of homogeneity and isotropy is also presented which reveals the presence of transverse energy transport and pressure transport in the part of the turbulence decay region where we take data (even though previous studies found mean flow and turbulence intensity profiles to be approximately homogeneous in much of the decay region). The exceptionally fast turbulence decay observed in the part of the decay region where we take data is consistent with the non-classical behaviour of the dissipation rate. Measurements with a regular square mesh grid as well as comparisons with active-grid experiments by Mydlarski & Warhaft (J. Fluid Mech., vol. 320, 1996, pp. 331–368) and Kang, Chester & Meveneau (J. Fluid Mech., vol. 480, 2003, pp. 129–160) are also presented to highlight the similarities and differences between these turbulent flows and the turbulence generated by our fractal square grid.

Download Full-text