Paper Title
Transient Investigation of Airflow Process Through Rectangular Cross-Ventilated Building With Two Vents in The Absence of Opposing Flow in Each of The Upper Opening

Abstract
Natural ventilation of building provides improvement of internal comfort and air quality conditions leading to a significant reduction of cooling energy consumption. Design of natural ventilation systems for many types of building is based on buoyancy forces. However, external wind flow can have significant effects on buoyancy- driven natural ventilation. A theoretical solution for transient investigation of airflow process through rectangular cross- ventilated building with two vents in the absence of opposing flow in each of the upper opening is obtained. A flow of this type represents a new class of boundary- layer flow problems in the building envelope. Moreover, this is an exact solution of the complete Navier- Stokes equations (including, buoyancy force term). The solutions for the velocity, temperature profiles together with volumetric airflow and mass transfer are obtained, and then evaluated numerically for several sets of values of the parameters; the effective thermal coefficient θ_0, the Prandtl number Pr. It is observed that, the greater vertical distance between the openings, and the greater temperature difference between the inside and the outside, the stronger is the effect of the buoyancy, the decrease in effective thermal coefficient θ_0, and increase in Prandtl number Pr results in an increase in velocity profiles U^* across the openings.for optimal ventilation. Keywords- Velocity, temperature profiles; Prandtl number; effective thermal coefficient