MODELLING OF MULTIPHASE FLOWS OVER SURFACE WITH PENETRABLE ROUGH RELIEF Yevgeniy A. Shkvar National Aviation University, Kyiv, Ukraine

Several kinds of turbulent flows associated with this investigation

Object of investigation is a boundary layer developing under conditions close to atmospheric (over rough surface and with presence of additive phase) a boundary layer developing under conditions close to atmospheric (over rough surface and with presence of additive phase) The atmosphere from space (source NASA) Background of the problem Brief information about typical dimensions and scales

The troposphere is a region of mixing, containing: 1)the largest percentage of the mass of the total atmosphere; 2)99 % of the water vapor in the atmosphere. 3)All weather phenomena occur within the troposphere. Atmosphere, its structure and phenomena Natural convective processes in the neighborhood of the land

Surface relief (roughness and penetrable roughness) There are many practically interested cases, when relief elements like 1.Land cover irregularities; 2.Forests; 3.Urban relief (buildings, streets, etc.) may be considered as a special kind of roughness distributed in the neighborhood of land and having penetrable effect

Sources of Air Pollution: 1.Smoke; 2.Natural air pollution; 3.Enterprise emissions; 4.Exhaust gas emissions; 5.Forest fires; 6.Radiation, chemical accidents. The atmosphere “lives” under strong influence of pollutions with different nature

Goal of the research Construct the simple model of the atmospheric boundary layer that will be able to account a rough relief influence on flow properties and pollution diffusion Accounting factors: 1. Surface is covered by rough relief with penetrable structure; 2. Flow can be heterogeneous; 3. Atmospheric pollutants have properties of scalar passive additives. Negligible factors: 1. Land Curvature; 2. Earth rotation, Coriolis effects; 3. Air compressibility; 4. Air stratification; 5. Radiation; 6. Heating; 7. Chemical and mechanical phase interaction

Investigated geometries of surface relief Streamlined surface Penetrable rough elements Flow direction

(1) (2) (3) (4) Continuity equation: Momentum equation in projections on x and y axes: Transfer equation of scalar additive concentration : Governing equations Here - the effective fluid volume,

Turbulence modeling Differential k-e approach (5) (5) (6) DIFFUSIVE COEFFICIENTS & DENSITY DETERMINATION (7)

Model details с  =0,09; с  1 =1,45; с  2 =1,92;  k =1;   =1,3 Near-wall modifications The set of model coefficients Source modifications (8) (9) - T. Maryuama

Turbulence modeling Algebraic approach (10) (11) (12) Here:,,,,, - the model’s coefficients ; lny U+ Smooth surface - V. Movchan’ formula

Boundary conditions Streamlined surface: Initial cross-section (input boundary):, Output boundaries of computational domain: Numerical Method Grid – nonuniform orthogonal staggered; + Leonard’, Zijlema’ 3-rd order schemes; Calculation procedure – Thomas algorithm. Method – SIMPLE

Testing of elaborated models Predictions of flow properties for several geometries of rough relief and their comparison with the experimental data

Flow behind penetrable obstacles Experimental data source: P. H. A. Barbosa; M. Cataldi; A. P. S. Freire, “Wind tunnel simulation of atmospheric boundary layer flows” J. Braz. Soc. Mech. Sci. vol.24 no.3 Rio de Janeiro July 2002 Flow phenomena: This flow was artificially thickened for making its parameters to be similar for typical atmospheric flows

Velocity profiles comparison in semi-logarithmic coordinates Investigated case: Flow behind rods array with 160 mm,U ∞ =3 m/s a) Experiments a) Experiments P. H. A. Barbosa; M. Cataldi; A. P. S. Freire (Brazil, 2002) ; b) Predictions on the base of this model

Skin friction coefficient vs. Re δ** Investigated case: Flow behind rods array with 160 mm,U ∞ =3 m/s Experiments Experiments P. H. A. Barbosa; M. Cataldi; A. P. S. Freire (Brazil, 2002 );

Flow over penetrable rough relief (short rough zone L rough =0.5m, ρ rough =0.25) CfCf δ*δ* H=δ*/δ**

Flow over penetrable rough relief (short rough zone L rough =0.5m, ρ rough =0.25) U, C k ε νtνtνtνt

Flow over penetrable rough relief (continuous rough zone L rough =6.5m, ρ rough =0.25) CfCf δ*δ* H=δ*/δ**

Flow over penetrable rough relief (continuous rough zone L rough =6.5m, ρ rough =0.25) U, C k ε νtνtνtνt

Flow over penetrable rough relief (rough array L rough =4x0.5m, ρ rough =0.25) CfCf δ*δ* H=δ*/δ**

Flow over penetrable rough relief (rough array L rough =4x0.5m, ρ rough =0.25) U, C k ε νtνtνtνt

Conclusion Presented model is able to account an influence of penetrable roughness on the turbulent flow properties; Presented model is able to account an influence of penetrable roughness on the turbulent flow properties; This model predicts an influence of rough relief on a scalar additive transfer; This model predicts an influence of rough relief on a scalar additive transfer; Algebraic approach to turbulence modeling is acceptable for this kind of viscous flows; Algebraic approach to turbulence modeling is acceptable for this kind of viscous flows; Penetrable roughness can be used as an effective tool of air protection. Penetrable roughness can be used as an effective tool of air protection.