Abstract
This paper reports the investigation of mean and turbulent flow characteristics of a two-dimensional plane diffuser. Both experimental and theoretical details are considered. The experimental investigation consists of the measurement of mean velocity profiles, wall static pressure and turbulence stresses. Theoretical study involves the prediction of downstream velocity profiles and the distribution of turbulence kinetic energy using a well tested finite difference procedure. Two models, viz., Prandtl's mixing length hypothesis and k-ɛ model of turbulence, have been used and compared. The nondimensional static pressure distribution, the longitudinal pressure gradient, the pressure recovery coefficient, percentage recovery of static pressure, the variation of U max/U bar along the length of the diffuser and the blockage factor have been valuated from the predicted results and compared with the experimental data. Further, the predicted and the measured value of kinetic energy of turbulence have also been compared. It is seen that for the prediction of mean flow characteristics and to evaluate the performance of the diffuser, a simple turbulence model like Prandtl's mixing length hypothesis is quite adequate.
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Abbreviations
- C ɛ1 , C ɛ2 ,C μ :
-
turbulence model constants
- F x :
-
body force
- k :
-
kinetic energy of turbulence
- l m :
-
mixing length
- L :
-
length of the diffuser
- u′, v′, w′ :
-
rms value of the fluctuating velocity
- u, v, w :
-
turbulent component of the velocity
- Ū :
-
mean velocity in the x direction
- Ū A :
-
average velocity at inlet
- U bar :
-
average velocity in any cross section
- U max :
-
maximum velocity in any cross section
- V :
-
mean velocity in the y direction
- W :
-
local width of the diffuser at any cross section
- x, y :
-
coordinates
- ɛ :
-
dissipation rate of turbulence
- ɛ m :
-
eddy diffusivity
- χ :
-
Von Karman constant
- λ :
-
mixing length constant
- μ l :
-
laminar viscosity
- μ eff :
-
effective viscosity
- v :
-
kinematic viscosity
- ρ :
-
density
- σ k :
-
effective Schmidt number for k
- σ ɛ :
-
effective Schmidt number for ɛ
- ψ :
-
stream function
- ω :
-
non dimensional stream function
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Ganesan, V., Suzuki, K., Narayana, P.A. et al. Investigations of mean and turbulent flow characteristics of a two dimensional plane diffuser. Experiments in Fluids 10, 205–212 (1991). https://doi.org/10.1007/BF00190390
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DOI: https://doi.org/10.1007/BF00190390