Articles
UNSTEADY COMPUTATIONAL STUDY OF AIRFLOW CHARACTERISTICS AROUND AN AGRICULTURAL STRUCTURE MODEL
Article number
952_22
Pages
185 – 190
Language
English
Abstract
Airflow characteristics such as air velocity and pressure are unsteady and undergo random high and low frequency fluctuations, when the flow is turbulent.
Turbulent flow is resulted, even in small air velocities, if a structure is present because it impedes the air flow.
This complex flow affects the external and the internal environment of agricultural structures.
The purpose of this work is the detailed analysis of airflow, in steady and unsteady state, for Reynolds number 700, around an agricultural structure model with arched geometry, which is placed in a wind tunnel.
The two-dimensional separated or reattached air flow, around the wind tunnel model is examined with the solution of Navier-Stokes equation, at steady and unsteady state, using the Galerkin finite element method.
The Reynolds number is calculated with respect to the model height and the inlet free stream velocity.
The different behavior of the airflow predictions around an arched type greenhouse, in steady and in unsteady state, are presented through the comparison of steady state streamlines and time-mean averaged streamlines (Re=700). Also, steady state stream-wise velocity is compared with instantaneous stream-wise velocity and time-mean averaged stream-wise velocity.
The time-mean averaged stream-wise velocity, which results from instantaneous values present more detailed predictions than the steady state stream-wise velocity.
Moreover, the time-mean averaged streamlines present smaller recirculation length of airflow than the steady state streamlines and thus simulate the airflow around the greenhouse more accurately.
Turbulent flow is resulted, even in small air velocities, if a structure is present because it impedes the air flow.
This complex flow affects the external and the internal environment of agricultural structures.
The purpose of this work is the detailed analysis of airflow, in steady and unsteady state, for Reynolds number 700, around an agricultural structure model with arched geometry, which is placed in a wind tunnel.
The two-dimensional separated or reattached air flow, around the wind tunnel model is examined with the solution of Navier-Stokes equation, at steady and unsteady state, using the Galerkin finite element method.
The Reynolds number is calculated with respect to the model height and the inlet free stream velocity.
The different behavior of the airflow predictions around an arched type greenhouse, in steady and in unsteady state, are presented through the comparison of steady state streamlines and time-mean averaged streamlines (Re=700). Also, steady state stream-wise velocity is compared with instantaneous stream-wise velocity and time-mean averaged stream-wise velocity.
The time-mean averaged stream-wise velocity, which results from instantaneous values present more detailed predictions than the steady state stream-wise velocity.
Moreover, the time-mean averaged streamlines present smaller recirculation length of airflow than the steady state streamlines and thus simulate the airflow around the greenhouse more accurately.
Authors
G.K. Ntinas, D.L. Kateris, V.P. Fragos, N.A. Malamataris, CH. Nikita-Martzopoulou
Keywords
arched type greenhouse, Navier-Stokes equations, steady state, time-mean averaged velocity
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