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Sattari et al. | http://dx.

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Gates are useful structures that are widely used in open channels for controlling discharge and water level. In this article, to study the flow passing under a gate, five gates with different‐shaped edges are numerically simulated. The contraction coefficient, discharge coefficient, pressure distribution behind the gate, and the pressure distribution on the channel bottom near the gate were investigated with models in free flow conditions. The analyses were performed for six water depths. The results show that the contraction coefficients for standard and jagged‐edged shapes increase with an increase in the a/E1 ratio (where a is the gate opening and E is the energy level), which matches the experimental results. For upward‐ and downward‐facing sharp edges and for rounded‐edged gates, the contraction coefficient decreases until a/E1 < 0.4 and increases for a/E1 > 0.4. Investigation of pressure distribution behind the gate and on the bottom of the channel under the gate shows that the position of maximum pressure is the same for all models, but its magnitude varies among different models. Comparison of numerical analysis results with experimental and theoretical data showed good agreement.

Radiative properties of interior surfaces can affect not only the building heat flux but also the indoor environment, the latter of which has not been thoroughly investigated. The aim of this study is to analyse the effect of surface emissivity on indoor air and surface temperature distributions in a test cabin with reflective interior surfaces. This was done by comparing experimental and simulation data of the test cabin with that of a normal cabin. This study employs transient computational fluid dynamics (CFD) using re-normalisation group (RNG) k-" model, surface-to-surface radiation model and an enhanced wall function. Boundary conditions were assigned to exterior surfaces under variable outdoor conditions. The numerical and the measurement results indicate that using interior reflective surfaces will affect the indoor air temperature distribution by increasing the vertical temperature gradient depending on the time of the day. CFD simulations with high spatial resolution results show increased interior surface temperature gradients consistent with the increased vertical air temperature gradient. The influence of reflective surfaces is potentially greater with higher indoor surface temperature asymmetry. The vertical indoor air temperature gradient and surface temperatures are important parameters for indoor thermal comfort.

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