scholarly journals Numerical Simulation of Random Cavitation Suppression Based on Variable NACA Airfoils

2021 ◽  
Vol 11 (24) ◽  
pp. 11618
Author(s):  
Weidong Shi ◽  
Zhouhao Shi ◽  
Zhanshan Xie ◽  
Qinghong Zhang ◽  
Yongfei Yang ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Working Conditions ◽  
Cavitation Erosion ◽  
Reference Value ◽  
Operating Conditions ◽  
Covering Surface ◽  
Hydraulic Machinery ◽  
Naca0012 Airfoil ◽  
Prone Area ◽  
Simulation Results

In order to suppress the cavitation of an airfoil under random operating conditions, a deformable covering was constructed in the cavitation prone area of the NACA0012 airfoil. By sensing the pressure difference between the inner and outer sides of the airfoil, the covering of the airfoil can be changed adaptively to meet the requirement of suppressing random cavitation of the airfoil. The simulation results show that the cavitation influence range of the airfoil with a shape memory alloy covering can be reduced by more than 70%, and the cavitation is well reduced and suppressed. Moreover, the backflow near the wall of the airfoil was reduced under random working conditions. When the maximum bulge deformation of the covering was between 3–6 mm, the airfoil produced a cavitation range only on the covering surface of the airfoil, and there was no cavitation erosion on other parts. This method with locally variable airfoil to suppress cavitation provides a good reference value for other hydraulic machinery to suppress cavitation.

scholarly journals Prefabricated Urban Underground Utility Tunnels: A Case Study on Mechanical Behaviour with Strain Monitoring and Numerical Simulation

2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Yonggang Xiao ◽  
Jubing Zhang ◽  
Jie Cao ◽  
Changhong Li
Keyword(s):  
Numerical Simulation ◽  
Working Conditions ◽  
Failure Modes ◽  
Mechanical Performance ◽  
Low Cost ◽  
Side Wall ◽  
Operating Conditions ◽  
Land Occupation ◽  
Depth Analysis ◽  
Simulation Results

The prefabricated urban utility tunnels (UUTs) have many advantages such as short construction period, low cost, high quality, and small land occupation. However, there is still a lack of in-depth analysis of the mechanical performance of the prefabricated urban utility tunnel (UUT) structure with bolted connections under different working conditions. In this paper, the force performance of a prefabricated UUT in Tongzhou District, Beijing, was studied under different working conditions using two methods: field monitoring and numerical simulation. The multichannel strain monitor was used for monitoring, and the internal wall concrete and bolt strain change data under the two conditions of installation and backfill were obtained. Combined with the construction process of the UUTs, a three-dimensional numerical model was established by COMSOL, where the build-in bolt assembly was used to simulate the longitudinal connection of the tunnel. The simulation results were compared with the measured data to verify the rationality of the computational model. The simulation results showed that the concrete and bolts on the inner wall of the tunnel work well under the two conditions of installation and backfilling; The deformation of the top plate of the prefabricated tunnel was approximately parabolic, with the largest vertical displacement (0.37 mm) in the middle and the most sensitive to the vertical load in the central part of the roof. The central portion of the side wall had the largest displacement (0.17 mm) in the inner concave. The tensile stress of bolt 3 increased the most (30.75 MPa) but was still much smaller than the yield strength of the bolt. The concrete and bolts of the UUT were found to work well through force analysis under operating conditions. In conclusion, analysis of structural forces and deformation failure modes will help design engineers understand the basic mechanisms and select the appropriate UUT structure.

scholarly journals Experimental Research and Numerical Simulation on Grouting Quality of Shield Tunnel Based on Impact Echo Method

2016 ◽  
Vol 2016 ◽  
pp. 1-10
Author(s):  
Fei Yao ◽  
Guangyu Chen ◽  
Jianhong Su
Keyword(s):  
Numerical Simulation ◽  
Finite Element ◽  
Working Conditions ◽  
Acoustic Impedance ◽  
Shield Tunnel ◽  
Test Results ◽  
Impact Echo ◽  
Simulation Results ◽  
The Impact ◽  
Impact Echo Method

To identify shield grouting quality based on impact echo method, an impact echo test of segment-grouting (SG) test piece was carried out to explore effect of acoustic impedance of grouting layers and grouting defects on impact echo law. A finite element numerical simulation on the impact echo process was implemented. Test results and simulation results were compared. Results demonstrated that, under some working conditions, finite element simulation results and test results both agree with theoretical values. The acoustic impedance ratio of SG material influenced the echo characteristics significantly. But thickness frequency could not be detected under some working conditions because the reflected energy is weak. Frequency feature under grouting defects was more complicated than that under no grouting defects.

Research on the CFD numerical simulation and process optimization of countercurrent–cocurrent dissolved air flotation

2019 ◽  
Vol 68 (5) ◽  
pp. 325-336
Author(s):  
Yonglei Wang ◽  
Wei Liu ◽  
Liping Tian ◽  
Ruibao Jia ◽  
Zhenqi Du ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Contact Zone ◽  
Process Optimization ◽  
Operating Conditions ◽  
Cocurrent Flow ◽  
Dissolved Gas ◽  
Dissolved Air Flotation ◽  
Simulation Results ◽  
Air Flotation ◽  
Dissolved Air

Abstract The countercurrent–cocurrent dissolved air flotation (CCDAF) process is a new type of air flotation process integrating countercurrent collision and cocurrent flow adhesion processes. The structural form of the CCDAF tank and its process parameters are the required conditions to achieve countercurrent collision and cocurrent adhesion. In this study, eight CCDAF tank process models were established with a flow rate of 0.5 m3/h. Flow field numerical simulation and process optimization of a CCDAF tank was conducted using Fluent software. The simulation results show that the optimal conditions for the CCDAF process are as follows: contact zone ascending velocity 10 mm/s, separation zone separation velocity 1.5 mm/s, dissolved gas pressure 0.45 MPa, and recirculating dissolved-gas distribution ratio R1/R2 1:1. Under these operating conditions, the flow state in the flotation tank is the most stable and the gas in the contact zone is evenly distributed. According to the simulation results, a 5 m3/h pilot plant was built. The structural dimensions were: B × L × H = 1,020 mm × 1,300 mm × 1,350 mm. The test results show that the CCDAF has a significant decontamination effect and is clearly superior to the cocurrent flow DAF process and countercurrent flow DAF process.

Numerical Simulation and Stereo PIV Test of Inner Flow in a Double Blades Pump

2011 ◽  
Author(s):  
Kai Wang ◽  
Houlin Liu ◽  
Shouqi Yuan ◽  
Minggao Tan ◽  
Yong Wang ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Velocity Field ◽  
Cfd Simulation ◽  
Research Work ◽  
Three Dimensional ◽  
Operating Conditions ◽  
Absolute Velocity ◽  
Operation Condition ◽  
Test Technique ◽  
Simulation Results

A double blades pump is widely used in sewage treatment industry, while at present the research on the internal flow characteristics of the double blades pump is very few. So, the CFD technology and the stereo PIV test technique are applied to study the inner flow in a double blades pump whose specific speed is 110.9. The commercial code FLUENT is used to simulate the inner flow in the double blades pump at 0.6Qd, 0.8Qd, 1.0Qd, 1.2Qd and 1.4Qd. The RNG k-ε turbulence model and SIMPLEC algorithm are used in FLUENT. According to the results of the three-dimensional steady numerical simulation, the distributions of velocity field in the impeller are obtained at the five different operating conditions. The analysis of the numerical simulation results shows that there is an obvious vortex in the impeller passage at off-design conditions. But the number, location and area of the vortex are different from each operation condition. In order to validate CFD simulation results, the stereo PIV is used to test the absolute velocity distribution in the double blades pump at Jiangsu University. The distributions of three-dimensional absolute velocity field at the above five different operating conditions are obtained by the PIV test, and the measured results are compared with the CFD simulation results. The comparison indicates that there are vortexes in impeller passages of the double blades pump under the five operating conditions. But as to the area of the vortex and the relative velocity values of the vortex core, there are some differences between the experiment results and the numerical simulation results. The research work can be applied to instruct the hydraulic design of double blades pumps.

scholarly journals Deactivation by sintering of the cobalt catalyst during the Fischer-Tropsch reaction

2019 ◽  
Vol 2 (1) ◽  
Author(s):  
Dounia Alihellal ◽  
Lemnouer Chibane ◽  
Mohamed El-Amine Slimani
Keyword(s):  
Numerical Simulation ◽  
Mathematical Model ◽  
Active Sites ◽  
Cobalt Catalyst ◽  
Reaction Rates ◽  
Operating Conditions ◽  
Molar Ratio ◽  
Fischer Tropsch ◽  
Simulation Results ◽  
By Products

In the present work, the deactivation by sintering of cobalt-based catalyst during Fischer-Tropsch synthesis at low temperature was studied by numerical simulation. For this purpose, a mathematical model was developed. The obtained simulation results allowed us to highlight and improve the understanding of the deactivation phenomena of cobalt-based Fischer-Tropsch catalysts by sintering. The main results also show that the sintering phenomenon is strongly dependent on the operating conditions, in particular, the temperature, the pressure, and the H2/CO molar ratio, as well as the reaction by-products such as water. The results obtained can, therefore, be used to understand more the sintering mechanism which may be linked to the change in the concentration of the active sites and the reaction rates.

Numerical Simulation Study on Self-Settlement Process of High Embankment

2013 ◽  
Vol 671-674 ◽  
pp. 1221-1224
Author(s):  
Yan Zhang ◽  
Yong Wang
Keyword(s):  
Numerical Simulation ◽  
Simulation Study ◽  
Reference Value ◽  
The Self ◽  
Maximum Settlement ◽  
Simulation Results ◽  
Embankment Height

This paper uses the FLAC software to simulate self-settlement of high embankment. Analysis and discussion on the simulation results are performed. The final results indicate that the self-settlement of high embankment can't be ignored, the maximum settlement within the embankment occurs at about （1/3～1/2）embankment height. This conclusion has a reference value for guiding the actual construction.

Frost Growth in Regenerative Heat Exchangers: Part II — Simulation and Discussion

2001 ◽  
Author(s):  
W. Shang ◽  
H. Chen ◽  
R. W. Evitts ◽  
R. W. Besant
Keyword(s):  
Experimental Data ◽  
Numerical Simulation ◽  
Spatial Distribution ◽  
Heat Exchangers ◽  
Operating Conditions ◽  
Time Duration ◽  
Regenerative Heat ◽  
Exhaust Temperature ◽  
Simulation Results ◽  
Frost Growth

Abstract In this paper a numerical simulation of frost growth is compared with experimental data that was taken for similar operating conditions as those for regenerative wheels. One set of simulation results for the frost growth model (Part I) is presented to predict frost growth in a regenerative wheel with a cold supply air temperature of −40 °C, a warm exhaust temperature of 20 °C and 50% relative humidity. Cyclic and longer time duration frost properties are presented along with the spatial distribution of frost within the wheel. It is concluded that frost blockage effects will become very significant in only 20 minutes of operation.

Numerical Simulation and Experimental Research on a Splash-Proof Water Injector

2011 ◽  
Vol 291-294 ◽  
pp. 2866-2870
Author(s):  
Zhong Yi Wang ◽  
Jia Han ◽  
Xu Yang ◽  
Tao Sun
Keyword(s):  
Numerical Simulation ◽  
Working Conditions ◽  
Domain Model ◽  
Calculation Methods ◽  
Two Phase ◽  
Simulation Research ◽  
Vof Model ◽  
Velocity Flow ◽  
Simulation Results ◽  
Experimental Researches

In this thesis, a model of water injector is established, which can prevent water from splashing when high-velocity flow pours into a container. With the periodic boundary, the 1/18 calculation domain model is built. Then two-phase flow numerical simulation research is done on the device with the steady VOF model. The influencing factors of water injector's performance and the variation laws under different working conditions are obtained. The reliability of the results is improved by comparing the results from different calculation methods with that from steady-state VOF method. And through the experimental researches on the splash-proof water injector, the accuracy of the numerical simulation results is validated.

Numerical Simulation of Air-Modulated Speaker with a Time-Dependent Shape Vocal Tract Model

2011 ◽  
Vol 138-139 ◽  
pp. 85-92
Author(s):  
He Feng Zhou ◽  
Xin Wu Zeng
Keyword(s):  
Numerical Simulation ◽  
Flow Field ◽  
Working Conditions ◽  
Sound Source ◽  
Vocal Tract ◽  
Time Dependent ◽  
Characteristic Parameters ◽  
Acoustic Characteristics ◽  
Modulation Model ◽  
Simulation Results

In order to explore the application of glottis’ deformable modulation model, used to simulate the human phonation process, in high power pneumatic speaker, a simulation model was established to model the flow field in the time-dependent shape vocal tract of air-modulated speaker. Characteristics of unsteady flow field in duct under typical working conditions were analyzed. The evolution process of pulsating sound source in the vocal tract was presented. The speaker’s characteristic parameters with different chamber pressures and modulated frequencies were investigated. The simulation results provided an useful guidance for possible application of improving the acoustic characteristics of pneumatic speaker.

Study on Resistance Characteristics of Marine Moisture Filter

2012 ◽  
Vol 466-467 ◽  
pp. 251-255
Author(s):  
Tao Sun ◽  
Guo Hui Zhang ◽  
Yi Zhang ◽  
Zhong Yi Wang
Keyword(s):  
Numerical Simulation ◽  
Performance Analysis ◽  
Flow Field ◽  
Simulation Method ◽  
Operating Conditions ◽  
Optimized Design ◽  
Ensemble Simulation ◽  
Three Stages ◽  
Simulation Results ◽  
Periodic Boundaries

Based on the periodic features of structure and flow field, two periodic boundaries are used to study the combined filter. The three stages filters are taken as integration for numerical simulation to acquire the resistance characteristics, which provide a reasonable foundation for performance analysis and optimized design of the filter. The resistance characteristics under different operating conditions acquired by experiment are compared with numerical simulation results of two periodic boundaries. The comparison validates the high precision of the ensemble simulation method.

Sign in / Sign up

Export Citation Format

Share Document