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EXPERIMENTAL & NUMERICAL INVESTIGATION OF WIND LOADS ON ROOFS FOR VARIOUS GEOMETRIES İsmail EKMEKÇİ, Mustafa ATMACA* and Hakan Soyhan The University of Sakarya, Engineering Faculty, Sakarya, Turkey * Marmara University,Technical Education Faculty, İstanbul,Turkey

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Background and Problem Statement Goals and Requirements Wind Tunnel and Measurements Experimental Roof Setup and Measurements Model and Calculation Method Experimental wind pressure coefficients Numerical wind pressure coefficients Comparison of Experimental & Numerical Results Conclusions Future Work Outline

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Wind Tunnel 1- Inlet part, 2- turbulence regulating chamber, 3- collector, 4- Section area, 5- Diffuser Adapter 6- Diffuser, 7- Outlet chamber, 8- Fan connection, 9- Fan cabin, 10- Fan, 11- Tunnel chassis, 12- Tunnel carrying wheel, 13- Velocity control unit, 14- Pitot tub, 15- Manometer, 16- Temperature probe, 17- Computer 18- Hot wire anemometer unit, 19- Oscilloscope, 20- Table, 21-Roof model, 22- Differential pressure sensor 23-Interface console 24- Wattmeter 25-Interface

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Experimental Roof Setup and Measurements

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Dimensions of the Roof Model Measurement Points

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Calculation Method for Measured Data Dimensionless pressure coefficients (C p ) [3] : Mean Wind Pressure (P mean ) and mean wind pressure coefficients ( ) :

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Numerical Calculations Effects of Mesh refinement in the 3-D simulations

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Mesh Class Maximum Number of Nods Maximum Number of Elements Mean Relative Error of the Cp Values % A48122366840,18 B58132953833,46 C69453557420,45 D8689455128,32 E117616316010,22 Effects of Mesh refinement on the Mean Error of the C p Values

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Effects of different turbulence models on the Pressure distribution (3-D simulations) Numerical Calculations

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Cross section computational domain

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Experimental wind pressure coefficients of α=10 o roof slope for several wind directions Φ=0 o Φ=30 o Φ=60 o Φ=90 o

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Experimental wind pressure coefficients of α=20 o roof slope for several wind directions Φ=0 o Φ=30 o Φ=60 o Φ=90 o

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Experimental wind pressure coefficients of α=30 o roof slope for several wind directions Φ=0 o Φ=30 o Φ=60 o Φ=90 o

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Numerical wind pressure coefficients of α=10 o roof slope for several wind directions Φ=0 o Φ=30 o Φ=60 o Φ=90 o

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Numerical wind pressure coefficients of α=20 o roof slope for several wind directions Φ=0 o Φ=30 o Φ=60 o Φ=90 o

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Numerical wind pressure coefficients of α=30 o roof slope for several wind directions Φ=0 o Φ=30 o Φ=60 o Φ=90 o

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Comparison of Experimental and Numerical Results for Mean Pressure Coefficients

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CONCLUSIONS - I Although it is obtained convenient pressure coefficient (Cp) values between experimental measurements and numerical computations, there are some inconveniences at some points. These deviations mostly occurred at roof corner points and back surfaces. Reasons for those differences are grid structure, mesh dimension, sample space dimension, insufficiency of selected turbulence model and could not making experimentally sensitive measures at these points. In numerical computation initially the effect of mesh structure is investigated. In numerical computations to investigate the effect of turbulence model 6, turbulence models (k-ε, RNG, Grimaji, Zero-equation, New k-ε, Shi-Zhu-Lumley) are tested at ANSYS-Flotron. Zero-equation turbulence model gives more accurate results comparing to other turbulence models. Hence Zero-equation model is used at all numerical computations.

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For 10 0 roof slope critical suction pressure coefficients are obtained for 0 0 and 30 0 wind directions at x/s=0,1 and x/s=0,5, for 60 0 and 90 0 wind directions at x/s=0,5. For 20 0 and 30 0 roofs slope critical pressure coefficients are obtained for 0 0, 30 0, 60 0 and 90 0 wind directions at x/s=0,5. For 10 0, 20 0 and 30 0 roofs slope, at 90 0 wind direction and at z/d=0.16, 0.33, 0.5, 0.66 suction pressure coefficients are observed smaller than other wind directions. For 10 0, 20 0 and 30 0 roofs slope at 60 0 and 90 0 wind directions maximum suction pressure coefficients have been obtained at z/d=0,83. For 30 0 roof slope at 0 0, 30 0 and 60 0 wind directions, positive pressure coefficients have been obtained between x/s=0-0,4. CONCLUSIONS - II

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