Sharif Digital Repository

Feasibility of an innovative buzz detection technique through measuring the static pressure outside a mixed-compression supersonic inlet is studied. The buzz is an instability phenomenon that occurs almost in all supersonic inlets. During the buzz, shock oscillation along with pressure and mass flow fluctuations affects the performance characteristics of the inlet. The main objective of this paper is to introduce a simple and easy-to-implement method for investigation of the buzz phenomenon in a supersonic inlet. The experimental data for far field-based are compared with those of the model-based one at free stream Mach numbers of 1.8, 2.0, and 2.2 and at zero degrees angle of attack for a... 

The flow over a supersonic inlet has been investigated experimentally and numerically at a free stream Mach number of 2 and a zero degree angle of attack. Wind tunnel tests were performed to obtain the performance parameters of the inlet and were used as a baseline and validation tools for the numerical code. A heat source was added to the flow field at a distance ahead of the inlet. The effect of heat source addition on the main performance parameters of the inlet is investigated numerically. Results show that the heat source considerably reduces drag coefficient; however, its effect on pressure recovery is not favorable. This unfavorable effect was then minimized by controlling heat source... 

Heat source addition to the axisymmetric supersonic inlet may improve the performance parameters, which will increase the inlet efficiency. In this investigation the heat has been added to the flow field at some distance ahead of an axisymmetric inlet by adding an imaginary thermal source upstream of cowl lip. The effect of heat addition on the drag coefficient, mass flow rate and the overall efficiency of the inlet have been investigated. The results show that heat addition causes flow separation, hence to prevent this phenomena, roughness has been added on the spike surface. However, heat addition reduces the drag coefficient and the inlet mass flow rate considerably. Furthermore, the... 

Experiments were conducted to study various kinds of Shock wave/Boundary Layer Interaction (SBLI) in an axisymmetric mixed-compression inlet. Experimental findings were compared and verified by numerical solutions where possible. Different types of SBLI relevant to the mixed-compression inlets are classified. Interactions of normal shock wave/boundary-layer at subcritical condition and in buzz condition are investigated using Schlieren and shadowgraph flow visualization as well as unsteady pressure recordings. The data is compared with the CFD predictions. Interactions of cowl lip reflected oblique shock and the terminal normal shock with the spike boundary-layer at both critical and... 

The flow through an axisymmetric supersonic mixed-compression air inlet has been simulated numerically to investigate the effects and the necessity of the three-dimensional (3D) modeling in comparison with the axisymmetric one. For this purpose, a supersonic inlet has been simulated numerically via axisymmetric and 3D CFD solvers, using the steady state Reynolds-averaged Navier-Stokes equations along with the SST k-ω turbulence model, for a free-stream Mach number of 2.0 and at zero degrees angle of attack. The grid for the 3D cases was a 14.4-degree sector, instead of a 360-degree domain one, with rotational periodic boundary condition for the side boundaries. The results show that both... 

The paper summarizes recent developments in boundary layer suction for high-speed air intakes. Bleed has been efficiently used in supersonic and hypersonic intakes for three primary reasons: to improve the performance of the intake, to reduce the starting Mach number of the intake, and to postpone the onset of buzz oscillations. A bleed system has many characteristics such as the bleed entrance and exit areas, bleed entrance slant angle and position, and bleed type (slot or porous and ram-scoop or flush). Each of these parameters has significant impacts on the intake performance and stability that have been reviewed in this study. In addition, the effectiveness of other flow control methods... 

The paper summarizes recent developments in boundary layer suction for high-speed air intakes. Bleed has been efficiently used in supersonic and hypersonic intakes for three primary reasons: to improve the performance of the intake, to reduce the starting Mach number of the intake, and to postpone the onset of buzz oscillations. A bleed system has many characteristics such as the bleed entrance and exit areas, bleed entrance slant angle and position, and bleed type (slot or porous and ram-scoop or flush). Each of these parameters has significant impacts on the intake performance and stability that have been reviewed in this study. In addition, the effectiveness of other flow control methods... 

Buzz phenomenon is shock oscillation ahead of the supersonic air intake when its mass flow rate is decreasing at offdesign condition. The buzz onset and the buzz cycle of an axisymmetric mixed-compression supersonic intake have been experimentally investigated through pressure recording and shadowgraph flow visualization. The intake was designed for a freestream Mach number of 2.0; however, tests were conducted for M∞ = 1.8, 2.0, and 2.2. All tests were performed at 0 deg angle of attack. Results show that there is a strong relation between the acoustic characteristics of the intake and the buzz fluctuations. This relation causes a new pattern for the buzz oscillations, large-amplitude... 

The performance of a supersonic mixed compression air intake has been investigated experimentally. The intake is of axisymmetric one and has been designed for a free stream Mach number of 2.0. The present work has two main goals, first to investigate the performance of the intake without boundary layer bleed at design and at off-design conditions and second to study the effects of a bleed slot on the intake performance. The intake has been tested at free stream Mach numbers of 1.8, 2.0, and 2.2 and at zero degrees angle of attack. Total pressure recovery, mass flow ratio, and flow distortion have been selected to assess the intake performance. The bleed slot is located upstream of the intake... 

The starting behavior of a supersonic axisymmetric mixed compression air intake was numerically investigated. The code solves Reynolds-Averaged Navier-Stokes equations using an explicit finite volume method in a structured grid by the Roe flux difference splitting scheme. Further, it uses the Baldwin-Lomax algebraic model to compute the turbulent viscosity coefficient. The correct method of surveying the intake starting problem and effects of several geometrical parameters such as: intake throat area, cowl lip roundness and spike surface curvature upstream of the throat on the starting and performance of the intake were studied. Results showed that correct combinations of the mentioned... 

Effects of various boundary-layer bleed locations on the stability of an axisymmetric supersonic inlet has been investigated experimentally. The bleeds were located on the inlet compression cone and were designed to improve the stability margin of the inlet. The main objective of the study was to identify the boundary-layer bleed location and its effectsonthe improvementofthestability marginofthe inlet.Inaddition,a buzz precursordetection methodology based on the rms level has been introduced. Experiments have been carried out on a mixed-compression inlet with a design Mach number of 2.0 and three different bleed locations at three freestream Mach numbers of 1.8, 2.0, and 2.2. All tests were... 

The performance of an axisymmetric supersonic mixed-compression air intake has been investigated experimentally. The intake has been designed for free stream Mach number of 2.0. This study has two main goals, firstly to investigate the performance of the intake without boundary-layer bleed in design and off-design conditions and secondly to study the effects of a slot bleed on the intake performance. The intake has been tested at free stream Mach numbers of 1.8, 2.0, and 2.2 and zero degree angle of attack. Total pressure recovery (TPR), mass flow ratio (MFR) and flow distortion (FD) have been selected parameters to assess the intake performance. The bleed slot is located upstream of the... 

In this study, three PE100 polyethylene materials with fairly different short chain branch distributions were used to characterize the relation between thermal properties and creep test failure time. The samples were thermally characterized using isothermal and non-isothermal differential scanning calorimetry (DSC). The three resins showed different behavior after fitting on the Avrami equation. N-100J2 sample, in which short chain branches (SCBs) are located on longer molecule chains, has a lower chain mobility and higher crystallization time, while N-100J1 has the opposite crystallization properties. Also, these samples had different Avrami index, n. Microstructural evaluation of these... 

In recent years, robotic rehabilitation has been utilized in treatment and recovery of patients with disabilities. In this paper, a novel design and kinematic analysis of a 4-DOF robot for upper-limb rehabilitation are proposed. The main novelty of this design is its mechanism for wrist and fingers motions which is added to the shoulder and elbow mechanism without any noticeable weight increase in the moving parts of the robot. For this purpose, a cable driven mechanism is implemented at the robot end-effector to move the wrist and fingers parts, and the corresponding actuators are placed at the base of the robot. © 2018 IEEE  

The procedures currently used for hepatitis B (HB) detection are not suitable for screening, clinical diagnosis, and point-of-care testing (POCT). Therefore, we developed and tested a QCM-based immunosensor by surface modification with AuNP-PEIs to amplify the signal and provide an oriented-immobilization surface. The AuNP-PEIs were characterized by ICP-Mass, UV/Vis, DLS, FE-SEM, and ATR-FTIR. After coating AuNP-PEIs on the gold electrode surface, anti-HBsAg antibodies were immobilized using NHS/EDC chemistry based on response surface methodology (RSM) optimization. The efficiency of the immunosensor was assessed by human sera and data were compared to gold-standard ELISA using...