Numerical Study on Air Movement as Affected by Obstacles in a Confined Chicken House

On the basis of the establishment of air movement equations in a confined ventilated chicken house, the governing equation, represented by the stream function and potential function, is deduced. According to the principle of energy variation, a plane finite element model with variable-node isoparameter elements is then developed. Importance is attached to the numerical solution of the equation in the form of stream function for a multiply connected region (i.e. there exist obstacles such as chicken bodies and the stacked-cages. ). Two approaches to determine the inner boundary conditions are proposed while adopting the fluid region supperposition method as follows; (1)zero circular tangent velocity condition. The integration of the tangent velocity in a closed inner boundary equals to zero; (2)minimum energy condition. The actual inner boundary conditions result in the total energy of the flow region to be minimum. Based on any of the above two conditions, a supplementary algebraic equation is thus established, which makes the problem well-defined.The differences in air distributions between cross ventilation and tunnel ventilation systems are compared with and without obstacles through computer simulations. The results show that air distributes very uniformly under tunnel ventilation,and obstacles inside the building have no obvious effects on the airflow pattern. However,air distribution under cross ventilation is extremely uneven, especially air velocity under the stacked-cages decreases greatly.