Aerospace Science and Technology
Mohammadreza Varshavi; Sahar Noori
Abstract
Air-breathing hypersonic flight is presumed by many of the savants in the field of aeronautical engineering as the last boundary of aerial vehicle design to be pushed back. An auspicious design configuration for the prospective hypersonic transport vehicles of the future is a “Waverider,” ...
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Air-breathing hypersonic flight is presumed by many of the savants in the field of aeronautical engineering as the last boundary of aerial vehicle design to be pushed back. An auspicious design configuration for the prospective hypersonic transport vehicles of the future is a “Waverider,” using the Scramjet engine cycle as its propulsive system. Two-dimensional CFD Analysis and case-to-case study of three pre-defined waverider configurations with 2-ramp, 3-ramp, and 4-ramp inlet geometries are carried out in the hypersonic flight regime of Mach numbers 5, 6, and 7. This is done in an attempt to study the single-oriented and also correlative-oriented impacts of increasing/decreasing the number of inlet ramps and increasing/decreasing the flight Mach number upon the behavior of final aerodynamic coefficients and ratios. The paramount outcome of the present work is the generation of some tables which can be utilized as primary guidelines for aeronautical design engineers who are designing waverider configurations on a preliminary basis.
Aerospace Science and Technology
G. R. Abdizadeh; Sahar Noori; Mohammad Saeedi; Hamidreza Tajik
Abstract
Designing flattened miniature heat pipes (FMHPs) for electronic devices is a challenging issue due to high heat flux and limited heat dissipation space. It requires understanding the combined effects of the sintered-grooved wick structure, double heat sources, and flat thickness on heat pipes' thermal ...
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Designing flattened miniature heat pipes (FMHPs) for electronic devices is a challenging issue due to high heat flux and limited heat dissipation space. It requires understanding the combined effects of the sintered-grooved wick structure, double heat sources, and flat thickness on heat pipes' thermal efficiency. Therefore, the aim of this study is to numerically investigate the effects of the FMHP with a hybrid wick on the thermal performance of its double heat sources acting as the CPU and GPU in notebook PCs. A transient 3D finite volume method was used to solve the governing equations and assisted boundary conditions. The cylindrical heat pipe with a 200 mm length and 6 mm outside diameter is flattened into 2, 2.5, 3, and 4 mm final thicknesses (FT). The obtained results show that the final critical thicknesses with the lowest thermal resistance are 2.5 and 3 mm for hybrid and grooved wick structures, respectively. Therefore, FMHP with hybrid wicks can be flattened about 8% more. Hybrid wick structures have the best effect on FMHP thermal performance at FT=2.5 mm
Aerospace Science and Technology
Sahar Noori; Armin Sheidani; Djavad Kamari
Abstract
In this study the effect of different configurations of three plates located in an air-filled container, which included vertical, horizontal and tilted, on coupled radiation and natural convection heat transfer has been numerically investigated. The side walls of the cavity were kept a constant temperature, ...
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In this study the effect of different configurations of three plates located in an air-filled container, which included vertical, horizontal and tilted, on coupled radiation and natural convection heat transfer has been numerically investigated. The side walls of the cavity were kept a constant temperature, while the upper and the lower walls were thermally insulated. In addition, non-uniform temperature distribution was applied to each of the plates. Moreover, in this study the effect of coupled heat transfer on flow separation and local Nu number was studied. The flow separation on the heated plates due to the thermal gradients was captured and the subsequent the effects were discussed. Also, the results reveal there are two main flow patterns known as separation of the convective flow and stretching of the CW vortex which are created by combined heat transfer. It was also demonstrated that these flow patterns are the main responsible for variations in the heat transfer.
Aerospace Science and Technology
Alireza Akbari; Sahar Noori; Payman Spahvand
Abstract
The main application of dynamic coefficients is in the flight path simulation and autopilot design of flying objects. This paper reveals a general process for calculating the roll damping coefficient of a typical airship. The process presented in this article has a step-by-step path that can be used ...
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The main application of dynamic coefficients is in the flight path simulation and autopilot design of flying objects. This paper reveals a general process for calculating the roll damping coefficient of a typical airship. The process presented in this article has a step-by-step path that can be used to calculate the roll dumping coefficient of all projectiles and flying objects. The method applied in this paper is fully numerical and the dynamic coefficient will be extracted from the Fluent software using the moving reference frame (MRF) techniques. In this process, first, the roll moment coefficient is extracted from the fluent using the moving reference frame technique, and then the roll damping coefficient will be calculated using some relations presented in this paper. At the beginning of the present work, the general process of calculating dynamic coefficients is discussed. This process is then used to calculate the dynamic coefficient of a typical geometry. The results of the present work and the process of calculating this coefficient, which is fully discussed in this article, can be used to calculate this coefficient in other flying objects with similar geometry. In order to validate the present article, the results of the present work are validated with the results of another article. Acceptable agreement of the results of the present work with references, proves the correctness of the process presented in this paper for calculating this dynamic coefficient.
Aerospace Science and Technology
Sahar Noori; Mohamad Saleh Afshar; Nima Karimi
Abstract
Airships usually have low cruising speed due to their large volume and high drag level. This makes the aerodynamic design of the vehicle, including the surfaces shape, the length-to-diameter ratio and the position of the fins, all very important. Furthermore, an important parameter in the vehicle aerodynamic ...
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Airships usually have low cruising speed due to their large volume and high drag level. This makes the aerodynamic design of the vehicle, including the surfaces shape, the length-to-diameter ratio and the position of the fins, all very important. Furthermore, an important parameter in the vehicle aerodynamic drag is determining the flow separation area at the rear of the air vehicle. The flow separation plays an essential role in the amount of drag and lift force, so the location of the fins and the design of the rear of the airship will be very important. By using both analytical and numerical methods, this study examines the aerodynamic efficiency of an airship in three different configurations, focusing on the location, type, and angle of attack of the fin, and compares analytical and numerical results. According to studies conducted among the types of fins, the cross-type will have the best performance among the fins in terms of lift-drag ratio. Also, moving the fins forward and distancing them from the rear of the vehicle disrupts the flow pattern at the rear of the vehicle and delays separation. This will improve aerodynamic efficiency and improve the lift-drag ratio of the vehicle.
