Models for characterising the aerodynamics of insect-proof screens from their geometric parameters

Abstract

This study characterised the geometric and aerodynamic parameters of 35 insect-proof screens with different weft and warp threads, with porosities ranging from 0.237 to 0.556 m2 m-2. The geometric parameters were assessed by analysing digital images,
\nand the aerodynamic parameters were determined using tests in a low-speed wind tunnel. Using the experimental measurements, four different models were developed and validated to estimate the aerodynamic parameters of an insect-proof screen from two or more of their geometric parameters: (i) to estimate the pressure drop coefficient Fφ based on the thread diameter Reynolds number (Red) and screen porosity φ [m2 m-2] Fφ=(0.4810002+11.5331/Red)×((1–φ2)/φ2) (R2 = 93.9% with a p-value = 0.000); (ii) estimating Fφ based on the screen thickness Reynolds number (Ret) and screen porosity φ [m2 m-2] Fφ = (0.475502+26.2114/Ret)×((1–φ2)/φ2) (R2 = 92.1% with a pvalue = 0.000); (iii) estimating screen permeability Kp=Dh2φ3/(2.0679 (1–φ)2)+3.8362×10–10 (R2=56.3%//56.2 % with a p-value<0.05) as a function of thread diameter Dh [m] and porosity φ [m2 m-2]; (iv) estimating the inertial factor Y=0.0571195+0.135966· Dh/Di (R2=58.1% with a p-value=0.0000) as a function of thread diameter [m] and the inner pore diameter Di [m]. These models gave improved accuracy compared with the previous models described in the literature. Models for aerodynamic parameters of the insect-proof screens Kp and Y based in their geometric characteristics are very important to simulate the effects of insect screens in ventilation studies using computational fluid dynamic (CFD) studies.