جستجوی مقالات مرتبط با کلیدواژه « cfd method » در نشریات گروه « فنی و مهندسی »

In recent decades, the use of natural energy sources such as light and solar energy in the field of construction and architecture has been very useful. The aim of this study was to investigate the effect of the location of openings on indoor air flow distribution for thermal comfort of users and natural ventilation, in addition to the distribution of daylight factor and pmv in space. Air circulation, wind speed, air temperature and daylight factor in 16 scenarios of placement of openings in a cube-shaped residential architecture was studied in the hot and dry climate of Yazd as a case study. In addition, in the present article, computer modeling method, library studies and field measurement were used. The analyses of air circulation, wind speed, air temperature and user satisfaction (PMV) were carried out using CFD method in Design Builder software and the amount of daylight factor (DF) distribution, uniformity rate (Uo) were analysed using Relux Software. The results indicated that the placement of one opening in the direction of the prevailing wind and the other two openings in its lateral directions provided the desired air flow and turbulence with appropriate speed and air circulation creating thermal comfort conditions for users in space. The amount of ventilation and air circulation in space, speed, temperature and distribution were balanced. In this scenario, the user satisfaction index (PMV) was 5% higher than other scenarios and the amount of daylight distribution and visual comfort (uniformity rate = 0.6) were in the appropriate range.

In this paper different approaches that mostly used in CFD simulation of reactive flows have been studied. Contents of the current study are included of turbulence reaction simulation by RANS, LES and DNS method and also simulation of multiphase flow by VOF, Eulerian-Eulerian and Eulerian-Lagrangian. Furthermore, simulation approaches of fast reaction processes respect to mixing time and common models and also their acceptable operational range have been presented in particular. Study of probability distribution function (PDF) models in which effect of reaction terms has been removed and also phenomenological models that are based on dominant micro-mixing time scale respect to reaction time scale have been considered.

Labyrinth spillways as appropriate hydraulic structure to pass PMF discharge have been considered. To replace existing spillways of reservoirs which in terms of capacity they are not hydraulically suitable، these types of spillways are recommended. In a certain width with similar head these spillways with nonlinear crest can pass greater discharges compare to spillways with frontal crest. The Labyrinth spillway is a type of hydraulic structure which can be used for the existing and new reservoirs. This structure is considered for hydraulic engineers as a good alternative to keep the water level of the reservoirs in an acceptable position when there is a limit on the maximum level of the water surface of the reservoir. The plan shape of the labyrinth spillway consists of broken lines in the form of triangular، trapezoidal، semi circular and rectangular with several repeating cycles. The main objective of using this type of spillway is to increase the flow capacity of the reservoir while keeping the crest and the water surface of the reservoirs in a reasonable level. The use of this type of reservoir goes back to the early 1920’s; however، the real studies and research in this field started form 1968. The majority of researches in this field are for those with triangular or trapezoidal in plan. The most advantages of using labyrinth spillway in the reservoirs and channels are as follows: 1- If the width of the spillway or channels cannot be chosen enough wide due to upstream or downstream site condition; 2- If the maximum level of the water in the reservoir during the flooding season is limited; 3- If it is desirable to provide larger water storage of the reservoir by making the crest level of the spillway higher without causing floodplain of upstream lands during high inflow to the reservoir; 4- If the capacity of the existing spillways are not large enough with respect to current standards of dams safety; 5- It is more economical due to the need of smaller discharge channel downstream of the spillway; and6- If the reservoir needs to have spillways with the gates to provide larger amount of water storage، in the case of labyrinth spillway the needs of the gates can be eliminated which is very advantageous both in terms of primary costs and maintenance costs. In this study by considering various angles of walls and lengths of nose different types of trapezoidal labyrinth spillways were designed. Applying Flow-3D software which is analytical software to solve equations of flow domain passed over spillway based on Eulerian viewpoint، numerical models were constructed. In order to model turbulence، the K-ε model in RNG state was used. Also to identify position of free surface profile، the VOF method was applied. To verify the results، experimental data of Tullis and Amanian (1995) was employed which the model results showed good agreement with the experimental data. Passing various discharges over the spillway variation of discharge coefficient was studied. It was showed with increase in length and angle of the spillway wall in flow direction the discharge coefficient would increase which is due to less interaction between the flow layers. This increase in small angles due to the reduction in over lapping layers is a considerable loss. At the end based on the obtained results a procedure to design a trapezoidal labyrinth spillway with choosing the angle of wall along the length of the nose was developed.