Procedural modeling buildings for finite element method simulation

Finite element methods for heat simulation at urban scale require mesh-volume models, where the meshing process requires a special attention in order to satisfy FEM requirements. In this paper we propose a procedural volume modeling approach for automatic creation of mesh-volume buildings, which are suitable for FEM simulations at urban scale. We develop a basic rule-set library and a building generation procedure that guarantee conforming meshes. In this way, urban models can be easily built for energy analysis. Our test-case shows a street created with building prototypes that fulfill all the requirements for being loaded in a FEM numerical platform such as Cast3M (www-cast3m.cea.fr).

Modeling and analysis of transient lubrication characteristic of the helicopter main transmission spiral bevel gears in point contacts

An engineering calculation model is introduced for point-contact elastohydrodynamic lubrication analysis of spiral bevel gears. This model can analyze transient lubrication characteristics of spiral bevel gears. The influence of the angle between the lubricant entrainment and the minor axis of the contact ellipse is included in this model. The contact parameters of the spiral bevel gear are calculated, which will change with time during the meshing process. The variation of lubricant film thickness during the meshing process of spiral bevel gears is unraveled. Due to the influence of entrainment velocity, the oil film thickness at the out mesh side is smaller than that at the enter mesh side under the same contact force. It is evident that the higher the pressure is, the larger the contact area will be. Meanwhile, the thickness of the oil film is reduced, and the oil film distribution in the contact area is relatively uniform. Taking helicopter main transmission spiral bevel gears as an example, this study finally calculates the distribution characteristics of the oil film thickness of the spiral bevel gear, and solves the lubrication performance of the spiral bevel gear under different working conditions.

HEAT TRANSFER AND FLUID FLOW INSIDE DUCT WITH USING FAN-SHAPE RIBS

A 2-D computational analysis is carried out to calculate heat transfer and friction factor for laminar flow through a rectangular duct with using fan–shape ribs as a turbulator. The types of rib shapes are imported on the heat transfer rate and fluid flow in heat exchangers. The present study makes use of fan-shaped ribs with two arrangements. The first arrangement was downstream fan–shape ribs (case 1) and upstream fan–shape ribs (case 2) is investigated. A commercial finite volume package ANSYS FLUENT 16.1 is used for solving the meshing process with continuity, momentum, and energy equations respectively to investigate fluid flow and heat transfer across the ribs surface. The Reynolds number (Re) range of (400 – 2250) with different relative roughness pitch (p/H= 0.17, 0.22, 0.27 and 0.32) at constant rib high (e/H). The results show that the heat transfers and friction increase with using ribs also, the results show that heat transfer Directly proportional to pitch ratio and Reynolds number. The Nusselt number enhancement by (12% -29%).

Simulation Research on Trapped Oil Pressure of Involute Internal Gear Pump

The main structure of an internal gear pump consisted of an internal gear pair, including an internal gear and an external gear. The internal gear pump had oil trapping phenomenon like other hydraulic gear pumps. In order to solve the oil trapping phenomenon of involute gear pump with internal meshing tooth profile, in this paper, the mathematical equation of gear outer contour is established according to the principle of generation method, and the variation law of the trapped oil area in meshing process is deduced by theoretical instantaneous flow rate obtained by scanning method. Then, the minimum trapped oil volume and unloading area are solved by the graphic method. Finally, based on fluid mechanics and dynamics, the trapped oil pressure model is obtained. The change of the trapped oil area and trapped oil pressure in a meshing cycle is simulated by MATLAB. The results show that the trapped oil area changes in a parabola, and the trapped pressure fluctuates in mountains and valleys. When the trapped area is the smallest, the trapped oil pressure reaches the peak at the corresponding corner. The research results can provide guidance for the development of high-performance internal gear pumps.

Dynamical wear prediction along meshing path in mixed lubrication of spiral bevel gears

Surfaces of gears under combined rolling and sliding motions may suffer a complicated wear process due to the transient time-varying effect along the meshing path. In this paper, a methodology for predicting the wear of tooth surfaces is developed for the spiral bevel gears. In the wear model, the machined surface roughness, mixed lubrication, friction, flash temperature and the dynamic behavior of gears are all considered. Tooth-Contact-Analysis (TCA) method is used to get the time-varying parameters of meshing points along the meshing path. By simulating real movement process, the material is removed according to the Arrhenius equation. First, the distribution of pressure and film thickness is obtained by solving the mixed EHL model. After that, the flash temperature can be computed by the point heat source integration method with the obtained pressure, film thickness and velocity vector. The material removal is based on surface temperature and sliding distance. The numerical results are compared to the ball-on-disk experiments to demonstrate the reasonableness of the present wear model. And it shows that the angle difference between velocity vectors has strong influences on the wear profile. Furthermore, the mechanism of surface wear evolution is investigated systematically in spiral bevel gears. The difference of the wear track between the pinion and gear surfaces is observed. Besides, in the meshing process of tooth surface, the wear along the meshing path is uneven, which appears to be much greater at the engaging-in and engaging-out areas. There is a position with maximum wear rate in the meshing process, and the position is affected by the load and speed.

Demand Analysis of Lubricating Oil in Spur Gear Pairs

Theoretical calculation and numerical simulation are used to investigate the lubricating oil demand of spur gears. In accordance with the function of lubricating oil during the meshing process, oil demand is regarded as the superposition of oil for lubrication and cooling. Oil for lubrication is calculated in accordance with meshing and elastohydrodynamic lubrication (EHL) theories. Oil for cooling is obtained from friction heat. The influence of different meshing positions on lubricating oil demand is analysed, and the effects of modulus, tooth number, transmission ratio, input speed and input torque on lubricating oil demand is investigated using a control variate method. Simulation results indicated that oil for lubrication and oil for cooling have two maxima each during a meshing circle. The influences of different gear parameters and working conditions on lubricating oil demand are compared. The results showed that the oil volume for lubrication increases and oil volume for cooling decreases as the modulus, tooth number and transmission ratio of the gear increase, the oil volume for lubrication and oil volume for cooling increases as the input speed and input torque increase.

Analisis Perbedaan Mesh Pada Simulasi Boiler PLTGU Tanjung Priok Berbasis CFD

Penelitian Analisis Perbedaan Mesh berbasis Computational Fluid Dynamic (CFD) ini dilakukan Pada Boiler PLTGU Tanjung Priok. Boiler atau reboiler dalam sistem PLTGU dikategorikan sebagai alat penukar kalor karena perpindahan panasnya dilakukan tanpa kontak langsung antara media pemanas dengan media yang dipanaskan. Fluida kerja pada boiler PLTGU Tanjung Priok berupa gas methane dan air. Penelitian ini bertujuan melihat jumlah pembagian elemen terhadap hasil simulasi dengan menggunakan dua model Studi konvergensi grid yaitu dengan grid kasar, dan yang paling optimal melalui hasil simulasi CFD. Metode yang digunakan mulai dari mendesain geometri boiler sesuai kondisi di lapangan menginput initial conditions dan boundry conditions. Data hasil penelitian yang sudah di lakukan pada simulasi boiler menunjukkan bahwa baik temperatur, tekanan dan kecepatan aliran memiliki nilai yang sama besar dan tidak di pengaruhi oleh pembagian elemen yang di lakukan pada saat proses meshing dari elemen yang paling kasar dengan jumlah total sebanyak 203.363 sampai pada tahap proses meshing dengan elemen teroptimal yang berjumlah sebanyak 1.491.428 berdasarkan hal tersebut maka proses simulasi yang dilakukan menjadi lebih efisien karena proses perhitungan data dari elemen yang lebih sedikit mendapatkan hasil yang sama dengan elemen yang lebih banyak. The research on Mesh Difference Analysis based on Computational Fluid Dynamic (CFD) was conducted at Tanjung Priok PLTGU Boiler. Boilers or reboilers in PLTGU systems are categorized as heat exchangers because the heat transfer is done without direct contact between the heating media and the heated media. The working fluid in the Tanjung Priok gas power plant boiler is in the form of methane gas and water. This study aims to look at the number of elements divided against the simulation results by using two grid convergence study models, namely with a coarse grid, and the most optimal through CFD simulation results. The method used starts from designing the boiler geometry according to the field conditions, inputting initial conditions and boundry conditions. Data from research that has been done on boiler simulations shows that both temperature, pressure and flow velocity have the same value and are not affected by the division of elements carried out during the meshing process of the most coarse elements with a total number of 203.363 up to the meshing process stage with the optimum elements totaling 1,491,428 based on this, the simulation process carried out becomes more efficient because the process of calculating data from fewer elements gets the same results with more elements.

Numerical Simulation of Gear Heat Distribution in Meshing Process Based on Thermal-structural Coupling

The thermal balance state of high-speed and heavy-load gear transmission system has an important influence on the performance and failure of gear transmission and the design of gear lubrication system. Excessive surface temperature of gear teeth is the main cause of gluing failure of gear contact surface. To investigate the gear heat distribution in meshing process and discuss the effect of thermal conduction on heat distribution,a finite element model of spur gear is presented in the paper which can represent general involute spur gears. And a simulation approach is use to calculate gear heat distribution in meshing process. By comparing with theoretical calculation, the correctness of the simulation method is verified, and the heat distribution of spur gear under the condition of heat conduction is further analyzed. The difference between the calculation results with heat conduction and without heat conduction is compared. The research has certain reference significance for dry gear hobbing and the same type of thermal-structural coupling analysis.

Calculation of Gear Meshing Stiffness Considering Lubrication

Gear meshing stiffness is the key parameter to study the gear dynamic performance. However, the study on the calculation of gear meshing stiffness considering lubrication, especially mixed lubrication, is still insufficient. Based on the three-dimensional linear contact mixed elastohydrodynamic lubrication model and the contact stiffness calculation method of rough surface, a method for calculating the gear meshing stiffness under mixed lubrication is proposed in this paper. According to the proposed calculation method, the effects of speed, external load, and roughness amplitude on gear meshing stiffness are further explored. The method can take into account the real rough surface topography and lubrication in the meshing process, so it may be more advantageous than the conventional method to some extent.