Effect of Aspect Ratios on the Performance Characteristics of Air Amplifier

2015 ◽  
Author(s):  
Jeong-Min Lee ◽  
Yi-Seul Jo ◽  
Sung-Min Kim ◽  
Youn-Jea Kim
Keyword(s):  
Shear Stress ◽  
Total Pressure ◽  
Applied Pressure ◽  
Flow Characteristics ◽  
Operating Conditions ◽  
Compressed Air ◽  
Turbulent Model ◽  
Aspect Ratios ◽  
Ansys Cfx ◽  
Induced Flow

In this study, the flow characteristics of the Coandă nozzle were studied with various values of the aspect ratio of induced flow inlet to outlet. Furthermore, four different applied pressure conditions of compressed air were also considered. Numerical analysis was performed using the commercial CFD code, ANSYS CFX with a shear stress transport (SST) turbulent model. The results of total pressure and velocity distributions were graphically depicted with various geometrical configurations and operating conditions.

scholarly journals Investigating the In-Flow Characteristics of Multi-Operation Conditions of Cross-Flow Fan in Air Conditioning Systems

Processes ◽  
2019 ◽  
Vol 7 (12) ◽  
pp. 959
Author(s):  
Weijie Zhang ◽  
Jianping Yuan ◽  
Qiaorui Si ◽  
Yanxia Fu
Keyword(s):  
Pressure Distribution ◽  
Flow Rate ◽  
Total Pressure ◽  
Air Conditioning ◽  
Pressure Pulsation ◽  
Flow Characteristics ◽  
Cross Flow ◽  
Operating Conditions ◽  
Aerodynamic Noise ◽  
Cross Flow Fan

Cross-flow fans are widely used in numerous applications such as low-pressure ventilation, household appliances, laser instruments, and air-conditioning equipment. Cross-flow fans have superior characteristics, including simple structure, small size, stable airflow, high dynamic pressure coefficient, and low noise. In the present study, numerical simulation and experimental research were carried out to study the unique secondary flow and eccentric vortex flow characteristics of the internal flow field in multi-operating conditions. To this end the vorticity and the circumferential pressure distribution in the air duct are obtained based on the performed experiments and the correlation between spectral characteristics of multiple operating conditions and the inflow state is established. The obtained results show that when the area of the airflow passage decreases while the area of the eccentric vortex area gradually increases, then the airflow of the cross-flow fan decreases, the outlet expands, and the flow pattern uniformity reduces. It was found that wakes form in the vicinity of the blade and the tail of the volute tongue, which generate pressure pulsation, and aerodynamic noise. The pressure distribution along the inner circumference shows that the total minimum pressure appears in the eccentric vortex near the volute tongue and the volute returns near the zone. Moreover, it was found that the total pressure near the eccentric vortex is significantly smaller than that of the main flow zone. As the flow rate decreases, the pressure pulsation amplitude of the eccentric vortex region significantly increases, while the static and total pressure pulsation amplitudes are gradually increased. Close to the eccentric vortex on the inner side of the blade in the volute tongue area, total pressure is low, total pressure on the outside of the blade is not affected, and pressure difference between the inner and outer sides is large. When the flow rate of the cross-flow fan is 0.4 Qd, there is no obvious peak at the harmonic frequency of the blade passage frequency. This shows that the aerodynamic noise is caused by the main unstable flow.

CFD Analysis of Circle Grid Fractal Plate Thickness on Turbulent Swirling Flow

2013 ◽  
Vol 465-466 ◽  
pp. 109-113 ◽  
Author(s):  
Bukhari Manshoor ◽  
Izzuddin Zaman ◽  
Mohamad Jaat ◽  
Amir Khalid
Keyword(s):  
Pressure Drop ◽  
Swirling Flow ◽  
Plate Thickness ◽  
Tangential Velocity ◽  
Flow Characteristics ◽  
Turbulent Model ◽  
Swirl Angle ◽  
Ansys Cfx ◽  
Flow Through ◽  
Different Thickness

In this paper, steady state, incompressible, swirling turbulent flow through circle grid fractal plate has been simulated. The aim of the simulation is to investigate an effect of the circle grid fractal plate thickness in order to reduce swirling due to swirl disturbance in pipe flow. The simulation and analysis were carried out using finite volume CFD solver ANSYS CFX. Three different thickness of fractal plate were used in the simulation work with the thickness of 1 mm, 3 mm and 6 mm. The simulation results were compared with the pressure drop correlation of BS EN ISO 5167-2:2003 and turbulent model used, standard k-ε model gave the best agreement with the ISO pressure drop correlation. The effects of circle grid fractal plate thickness on the flow characteristics which are swirl angle and tangential velocity have been investigated as well.

scholarly journals Effect of Rotational Speed Variation on the Flow Characteristics in the Rotor-Stator System Cavity

2021 ◽  
Vol 11 (22) ◽  
pp. 11000
Author(s):  
Zhizhou Zhao ◽  
Wenwu Song ◽  
Yongxin Jin ◽  
Jiaxing Lu
Keyword(s):  
Reynolds Number ◽  
Shear Stress ◽  
Rotational Speed ◽  
Geometric Model ◽  
Flow Characteristics ◽  
Test Model ◽  
Rotating Speed ◽  
Ansys Cfx ◽  
Clearance Flow ◽  
Rotor Wall

In this paper, to study the effect of dynamic and static interference of clearance flow in fluid machinery caused by changes in rotational speed, the model was simplified to a rotor-stator system cavity flow. Investigating the flow characteristics in the cavity by changing the rotor speed of the rotor-stator system is of considerable significance. ANSYS-CFX was applied to numerically simulate the test model and the results were compared with the experimental results of the windage torque of the rotor-stator system. The inlet flow rate and geometric model remained unchanged. With an increase in the rotating Reynolds number, the shear stress on the rotor wall gradually increased, and the maximum gradient was within l* < 0.15. In addition to the shear stress, the tangential Reynolds stress Rrθ contributed partly to the torque on the rotor wall. The swirling vortex formed by entrainment in the cavity of the rotor-stator system tended to separate at ReΦ= 3.53 × 106. As the rotating Reynolds number continued to increase, the secondary vortex finally separated completely. The strength of the vortex in the rotor turbulent boundary layer decreased with an increase in the rotating speed, but the number of vortex cores increased with the increase of speed. Depending on the application of the fluid machine, controlling the rotating speed within a reasonable range can effectively improve the characteristics of the clearance flow.

scholarly journals Simulation and Analysis of a Turbulent Flow Around a Three-Dimensional Obstacle

2019 ◽  
Vol 13 (3) ◽  
pp. 173-180
Author(s):  
Lamia Benahmed ◽  
Khaled Aliane
Keyword(s):  
Shear Stress ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Turbulence Models ◽  
Governing Equations ◽  
Complex Behaviour ◽  
Ansys Cfx ◽  
Recirculation Zones ◽  
Volume Method ◽  
Calculation Code

Abstract The study of flow around obstacles is devised into three different positions: above the obstacle, upstream of the obstacle, and downstream of the latter. The behaviour of the fluid downstream of the obstacle is less known, and the physical and numerical modelling is being given the existence of recirculation zones with their complex behaviour. The purpose of the work presented below is to study the influence of the inclined form of the two upper peaks of a rectangular cube. A three-dimensional study was carried out using the ANSYS CFX calculation code. Turbulence models have been used to study the flow characteristics around the inclined obstacle. The time-averaged results of contours of velocity vectors <V>, cross-stream <v> and stream wise velocity <u> and streamlines were obtained by using K-ω shear -stress transport (SST), RANG K-ε and K-ε to model the turbulence, and the governing equations were solved using the finite volume method. The turbulence model K-ω SST has presented the best prediction of the flow characteristics for the obstacle among the investigated turbulence models in this work.

Effect of Different Airfoils on Performance of Axial Fan

2014 ◽  
Vol 945-949 ◽  
pp. 928-934
Author(s):  
Bang Lun Zhou ◽  
Jian Ping Yuan ◽  
Zhi Xia He ◽  
Feng Hong
Keyword(s):  
Kinetic Energy ◽  
Turbulent Kinetic Energy ◽  
Total Pressure ◽  
Great Influence ◽  
Leading Edge ◽  
Operating Conditions ◽  
Axial Fan ◽  
Blade Thickness ◽  
Ansys Cfx ◽  
Airfoil Blades

Airfoil has great influence on the performance of axial fan. In order to study performance of axial fan. Four kinds of airfoils have been applied to optimize the impeller of axial fan. The 3D internal flows of the axial fan under different operating conditions were simulated based on a steady numerical method in ANSYS CFX 14.5. The results show that the curve of total pressure of the fan with LS airfoil blades is slightly steeper, and that of the fan with CLARK-Y(C=11.7%) (C is the blade thickness ratio) airfoil blades is relatively flat. The total pressure of the axial fan with CLARK-Y(C=11.7%) blades is highest among others. While achieving the highest efficiency in all the operating conditions except the lowest flow rate. Moreover, the blades loading of the CLARK-Y(C=11.7%) airfoil blades fan is entirely more uniform than that in others. The turbulent kinetic energy distribution on the leading edge of blades shows that the axial fan with CLARK-Y(C=11.7%) airfoil blades fan can improve the turbulent kinetic energy effectively.

Influence of Nozzle Aspect Ratio and Orientation on Flow Characteristics of Multiple Elliptic Jets

2019 ◽  
Author(s):  
Hiroshi Teramoto ◽  
Takahiro Kiwata ◽  
Kako Yajima
Keyword(s):  
Flow Characteristics ◽  
The Self ◽  
Equivalent Diameter ◽  
Hot Wire ◽  
Ambient Fluid ◽  
Aspect Ratios ◽  
Multiple Jets ◽  
Induced Flow ◽  
The Mean ◽  
Axis Switching

Abstract An experimental study is conducted to investigate the flow characteristics of multiple elliptic jets issuing from a 6 × 6 nozzle array at a relatively low-Reynolds number (Re = 4.3 × 103). Two aspect ratios of the multiple elliptic nozzles (equivalent diameter, de, of a nozzle was 6 mm), namely a/b = 2.25 and 6.25, where a and b are the radii of the major and minor axes of an elliptic nozzle, respectively, and two nozzle azimuthal orientations, namely the same and alternate azimuthal orientation arrangements, were used. The mean and fluctuating velocities were measured using a constant-temperature hot-wire anemometer. The multiple jets located at the side of the ambient fluid were stretched due to interactions between the self-induced flow of an elliptic vortex ring and the secondary flow caused by the entrainment of the ambient fluid. For a/b = 2.25, axis switching occurred only once in the range of 1 &lt; x/de ≤ 3 for both nozzle azimuthal orientations. For a/b = 6.25 and the same azimuthal orientation arrangement, axis switching occurred only once at 3 &lt; x/de ≤ 5; axis switching did not occur for the alternate azimuthal orientation arrangement. Thus, the flow characteristics of multiple elliptic jets are influenced by the azimuthal orientation of adjoining nozzles.

Numerical Study of Gaseous Microchannel Flows on the Dimensional and Physical Effects

2009 ◽  
Author(s):  
Kuan-Hung Lin ◽  
Jiunn-Chi Wu
Keyword(s):  
Friction Factor ◽  
Numerical Study ◽  
Pressure Ratio ◽  
Slip Flow ◽  
Applied Pressure ◽  
Flow Characteristics ◽  
Velocity Slip ◽  
Analytic Solutions ◽  
Transition Flow ◽  
Aspect Ratios

In this article, we perform a series of simulations to analyze the gaseous flow in two-dimensional (2D) and three-dimensional (3D) microchannels. The geometry effects of entrance and exit, applied pressure ratios and rarefaction effects on the flow characteristics are thoroughly investigated. In addition, a modified Poiseuille number correlation for air flows is obtained. This calculation solves the compressible Navier-Stokes and energy equations under velocity slip and temperature jump conditions with varying inlet to outlet pressure ratios (from 1.76 to 20), the outlet Knudsen numbers (from 0 to 0.22) and the aspect ratios (from 0 to 0.47). The calculated mass flow rate, pressure distribution and friction factor are compared with analytic solutions and experimental data in both the slip flow and earlier transition flow regimes. In the case of higher applied pressure ratio, both experiments and numerical modeling show pressure drop at upstream and downstream. Finally, we discuss the adequacy of the friction factor correlation for the 2D flow and the 3D flow in microchannels with both inlet and outlet chambers.

scholarly journals Assessing Machine Learning versus a Mathematical Model to Estimate the Transverse Shear Stress Distribution in a Rectangular Channel

Mathematics ◽  
2021 ◽  
Vol 9 (6) ◽  
pp. 596
Author(s):  
Babak Lashkar-Ara ◽  
Niloofar Kalantari ◽  
Zohreh Sheikh Khozani ◽  
Amir Mosavi
Keyword(s):  
Shear Stress ◽  
Stress Distribution ◽  
Fuzzy Inference ◽  
Rectangular Channel ◽  
Tsallis Entropy ◽  
Shear Stress Distribution ◽  
Data Series ◽  
Shear Stresses ◽  
Inference System ◽  
Aspect Ratios

One of the most important subjects of hydraulic engineering is the reliable estimation of the transverse distribution in the rectangular channel of bed and wall shear stresses. This study makes use of the Tsallis entropy, genetic programming (GP) and adaptive neuro-fuzzy inference system (ANFIS) methods to assess the shear stress distribution (SSD) in the rectangular channel. To evaluate the results of the Tsallis entropy, GP and ANFIS models, laboratory observations were used in which shear stress was measured using an optimized Preston tube. This is then used to measure the SSD in various aspect ratios in the rectangular channel. To investigate the shear stress percentage, 10 data series with a total of 112 different data for were used. The results of the sensitivity analysis show that the most influential parameter for the SSD in smooth rectangular channel is the dimensionless parameter B/H, Where the transverse coordinate is B, and the flow depth is H. With the parameters (b/B), (B/H) for the bed and (z/H), (B/H) for the wall as inputs, the modeling of the GP was better than the other one. Based on the analysis, it can be concluded that the use of GP and ANFIS algorithms is more effective in estimating shear stress in smooth rectangular channels than the Tsallis entropy-based equations.

Unsteady simulations of migration and deposition of fly-ash particles in the first-stage turbine of an aero-engine

2021 ◽  
pp. 1-21
Author(s):  
Z. Hao ◽  
X. Yang ◽  
Z. Feng
Keyword(s):  
Fly Ash ◽  
Film Cooling ◽  
Particle Deposition ◽  
Flow Characteristics ◽  
Leading Edge ◽  
Velocity Model ◽  
Operating Conditions ◽  
Inlet Temperature ◽  
Internal Cooling ◽  
Aero Engine

Abstract Particulate deposits in aero-engine turbines change the profile of blades, increase the blade surface roughness and block internal cooling channels and film cooling holes, which generally leads to the degradation of aerodynamic and cooling performance. To reveal particle deposition effects in the turbine, unsteady simulations were performed by investigating the migration patterns and deposition characteristics of the particle contaminant in a one-stage, high-pressure turbine of an aero-engine. Two typical operating conditions of the aero-engine, i.e. high-temperature take-off and economic cruise, were discussed, and the effects of particle size on the migration and deposition of fly-ash particles were demonstrated. A critical velocity model was applied to predict particle deposition. Comparisons between the stator and rotor were made by presenting the concentration and trajectory of the particles and the resulting deposition patterns on the aerofoil surfaces. Results show that the migration and deposition of the particles in the stator passage is dominated by the flow characteristics of fluid and the property of particles. In the subsequential rotor passage, in addition to these factors, particles are also affected by the stator–rotor interaction and the interference between rotors. With higher inlet temperature and larger diameter of the particle, the quantity of deposits increases and the deposition is distributed mainly on the Pressure Side (PS) and the Leading Edge (LE) of the aerofoil.

scholarly journals Shear Stress-Triggered Deformation of Microparticles in a Tapered Microchannel

Polymers ◽  
2020 ◽  
Vol 13 (1) ◽  
pp. 55
Author(s):  
Cheolheon Park ◽  
Junghyun Bae ◽  
Yeongjae Choi ◽  
Wook Park
Keyword(s):  
Shear Stress ◽  
Void Fraction ◽  
Applied Pressure ◽  
Microfluidic Channel ◽  
Volume Index ◽  
Effective Volume ◽  
Particle Deformation ◽  
Polyethylene Glycol Diacrylate ◽  
Glycol Diacrylate ◽  
Deformation Ratio

We demonstrate that it is possible to produce microparticles with high deformability while maintaining a high effective volume. For significant particle deformation, a particle must have a void region. The void fraction of the particle allows its deformation under shear stress. Owing to the importance of the void fraction in particle deformation, we defined an effective volume index (V*) that indicates the ratio of the particle’s total volume to the volumes of the void and material structures. We chose polyethylene glycol diacrylate (Mn ~ 700) for the fabrication of the microparticles and focused on the design of the particles rather than the intrinsic softness of the material (E). We fabricated microparticles with four distinct shapes: discotic, ring, horseshoe, and spiral, with various effective volume indexes. The microparticles were subjected to shear stress as they were pushed through a tapered microfluidic channel to measure their deformability. The deformation ratio R was introduced as R = 1−Wdeformed/Doriginal to compare the deformability of the microparticles. We measured the deformation ratio by increasing the applied pressure. The spiral-shaped microparticles showed a higher deformation ratio (0.901) than those of the other microparticles at the same effective volume index.

Sign in / Sign up

Export Citation Format

Share Document