LES-Based Numerical Simulation of Flow Noise for UUV with Full Appendages

2013 ◽  
Vol 631-632 ◽  
pp. 879-884 ◽  
Author(s):  
Shi Yao ◽  
Pan Guang ◽  
Huang Qiao Gao
Keyword(s):  
Numerical Simulation ◽  
Noise Level ◽  
Geometric Model ◽  
Simulation Method ◽  
Underwater Vehicle ◽  
Computational Method ◽  
Computational Region ◽  
Flow Noise ◽  
Unmanned Underwater Vehicle ◽  
Eddy Simulation

Numerical simulation of flow field and flow noise was carried out on SUBOFF with Lighthill acoustical analogy and large eddy simulation method. The results agreed well with the numerical and experimental results obtained from published literature. The validation of the computational method of flow noise used in this paper was carried out. The geometric model was established for the unmanned underwater vehicle with full appendages and the flow field’s computational region discretization was carried out by using structural grid. Numerical simulation of flow noise for unmanned underwater vehicle with full appendages was taken. The numerical results show that the angle of attack has little effect on the flow noise level of the vehicle while the angle ranged from 0° to 4°. Compared with the “＋”-type rudders, the flow noise level of the underwater vehicle with “X”-type rudders is about 3dB lower.

Three-Dimensional Numerical Simulation of the Flow around Two Side-by-Side Cylinders of Different Diameters

2014 ◽  
Vol 721 ◽  
pp. 199-202
Author(s):  
Zhen Xiao Bi ◽  
Zhi Han Zhu
Keyword(s):  
Numerical Simulation ◽  
Flow Direction ◽  
Three Dimensional ◽  
Cross Flow ◽  
Simulation Method ◽  
Scale Model ◽  
Hydrodynamic Characteristics ◽  
Eddy Simulation ◽  
Drag And Lift ◽  
Different Diameters

This paper presents the calculation of hydrodynamic characteristics of two side-by-side cylinders of different diameters in three dimensional incompressible uniform cross flow by using Large-eddy simulation method based on dynamical Smagorinsky-Lilly sub-grid scale model. Solution of the three dimensional N-S equations were obtained by the finite volume method. The numerical simulation focused on investigating the characteristic of the pressure distribution (drag and lift force), vorticity field and turbulence Re=. Results shows that, the asymmetry of the time –averaged velocity distribution in the flow direction behind the two cylinders is very obvious; the frequency of eddy shedding of the small cylinder is about twice of the large one. The turbulence of cylinders is more obvious.

The Research of Subspan Oscillation and Configuration of Spacer for Transmission Line

2012 ◽  
Vol 614-615 ◽  
pp. 1855-1861
Author(s):  
Yu Xian Di ◽  
Kuan Jun Zhu ◽  
Cao Lan Liu
Keyword(s):  
Numerical Simulation ◽  
Transmission Lines ◽  
Simulation Method ◽  
Computational Method ◽  
Analysis Model ◽  
Element Analysis ◽  
Finite Element Analysis Model ◽  
The Finite Element Analysis ◽  
Computer Aided ◽  
Calculation Procedures

Based on the summarization of domestic and foreign experience, the computational method of spacer configuration was developed in order to depress sub-span oscillation principally. The requirements of the reverse recovery characteristics were considered. The computer-aided calculation procedures were programmed. The finite element analysis model of sub-span oscillation for cable-spacer system was established. The inherence modal and amplitude for sub-span oscillation of bundled transmission lines were calculated by using numerical simulation method. The dynamic configurations were analyzed by using the parameters of the cable and spacer obtained from vibration testing.

scholarly journals Hybrid Numerical Simulation of Jet Blast Distance of a Departing Aircraft

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Xin He ◽  
Yaqing Chen ◽  
Yilong Ma ◽  
Dengfeng Hu ◽  
Haoran Gao
Keyword(s):  
Numerical Simulation ◽  
Numerical Simulations ◽  
Turbulence Model ◽  
Internal Flow ◽  
Aircraft Engine ◽  
Simulation Method ◽  
Detached Eddy Simulation ◽  
Eddy Simulation ◽  
Numerical Simulation Method

A hybrid numerical simulation method was established by combining the Spalart-Allmaras (SA) turbulence model and detached eddy simulation (DES). Numerical simulations were carried out to model cold and hot spray conditions of a nozzle without considering the internal flow of an engine to determine jet conditions. Analysis results show that the calculated hot spray results more in line with the reality. The jet effect of a typical aircraft engine was simulated numerically to determine the distance influenced by the jet blast from a departing aircraft engine.

Numerical Simulation of Instantaneous Wave-Free Ratio of Stenosed Coronary Artery

2019 ◽  
Vol 16 (03) ◽  
pp. 1842009 ◽  
Author(s):  
Wenxin Wang ◽  
Boyan Mao ◽  
Bao Li ◽  
Xi Zhao ◽  
Chensi Xu ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Coronary Artery ◽  
Functional Performance ◽  
Geometric Model ◽  
False Positive Rate ◽  
Three Dimensional ◽  
Cost Benefit ◽  
Simulation Method ◽  
Patient Specific ◽  
Three Dimensional Model

Instantaneous wave-free ratio (iFR), an invasive index of coronary artery tree, can evaluate the functional performance of vascular stenosis without pharmacological vasodilators. The noninvasive assessment of diameter stenosis (DS) obtained from coronary computed tomography angiography (CTA) has high false positive rate in contrast to iFR. The aim of this study was to develop a numerical simulation method that predicts the iFR and noninvasively assess the myocardial ischemia. Based on the CTA images, a patient-specific three-dimensional model of the aorta and coronary arteries were reconstructed. A stenosis was created in the left anterior descending artery (LAD) by reducing the DS of geometric model (40%, 50%, 60%, 75% and 90%). The patient-specific LPM boundary condition were set up to compute iFRct value during the wave-free period at the resting condition. The computed pressure and flow of coronary artery were realistic as compared to literature data. In contrast to invasive iFR, the iFRct can make a cost-benefit balance in terms of clinical cost and patient’s health.

The Analysis of Temperature and Displacement Coupling in Freeze-Thaw Process of Soil

2011 ◽  
Vol 97-98 ◽  
pp. 192-198
Author(s):  
Shu Guang Hou
Keyword(s):  
Numerical Simulation ◽  
Temperature Field ◽  
Numerical Computation ◽  
Geometric Model ◽  
Simulation Method ◽  
Frozen Soil ◽  
Displacement Fields ◽  
Soil Frost ◽  
Freeze Thaw ◽  
Thaw Settlement

Through the coupling analysis of temperature and displacement fields in freeze-thaw process of soil by ABAQUS software, a numerical simulation method of the two fields coupling in freeze-thaw process of soil is put forward. In computation, the temperature field is analyzed firstly, and then the physico-mechanical parameters are defined as functions of temperature field. The geometric model and boundary conditions of numerical simulation are identical with these in laboratorial tests. By comparing the computation results of soil freeze-thaw process with its laboratorial test results, it was found that on the curve of soil freeze-thaw process obtained from laboratorial tests there is a short frost-swelling phenomenon at the initial stage of freeze-thaw process, and then is continuous thaw condition, but on the numerical computation curve, the reflect of soil frost swelling stage isn’t obvious. With the exception of this the numerical computation result and laboratorial test result are more identical. The frost-swelling quantum is very small, so the main expression of overall deformation of soil is thaw-settlement deformation. Therefore the frost swelling phenomenon doesn’t influence the end quantum of settlement. For this reason, the computing method introduced in this paper can be used to conduct numerical simulation of the thaw-settlement of frozen soil and to a certain extent guide the designs of subgrade and pavement in permafrost zones.

Numerical Simulation Method for Unsteady Wind Field around Building

2011 ◽  
Vol 243-249 ◽  
pp. 521-526
Author(s):  
Qi Li ◽  
Qing Shan Yang ◽  
Yu Fen Jin
Keyword(s):  
Numerical Simulation ◽  
Wind Field ◽  
Complex Geometry ◽  
Simulation Method ◽  
Computer Code ◽  
Measure Data ◽  
Eddy Simulation ◽  
Wind Structure ◽  
Time Marching ◽  
Texas Tech University

A large eddy simulation algorithm for numerically calculating unsteady wind field around complex geometry building was given. In this algorithm, a curvilinear coordinate system was used to formulate the numerical model, so the complex wind-structure interface could be described precisely. Governing equations were discretized by central differencing schemes with co-located grids. The convection velocity was interpolated by using Rhie-Chow method in order to avoid the inherent odd-even decoupling problem. A common Maker and Cell (MAC) scheme was used to split the velocity-pressure linkage in Navier-Stockes (NS) equation. An explicit Adams-Bashforth differencing scheme was applied for time marching. A corresponding computer code was developed and was validated by performing on simulation of wind field around full-scale Texas Tech University (TTU) building model. Furthermore, the simulation results were compared with corresponding field measure data and wind-tunnel experiment results reported by other authors. The comparison showed that this algorithm is feasible for numerical simulation of unsteady wind field around buildings.

scholarly journals Coupled vibration of piezoelectric-based propeller blades for a novel unmanned underwater vehicle

2020 ◽  
Vol 12 (4) ◽  
pp. 168781402091658
Author(s):  
Daohua Lu ◽  
Chong Li ◽  
Jia Wang ◽  
Jiwen Fang
Keyword(s):  
Dynamic Performance ◽  
Design Procedure ◽  
Simulation Method ◽  
Underwater Vehicle ◽  
Dynamic Responses ◽  
Matlab Simulation ◽  
Coupled Vibration ◽  
Unmanned Underwater Vehicle ◽  
Lagrange’S Equation ◽  
Propeller Blades

To reduce the vibration of the propeller blades, a novel unmanned underwater vehicle–integrated piezoelectric additive manufacturing technology is proposed in this article. The operating principle and design procedure of the proposed unmanned underwater vehicle are illustrated. Utilizing piezoelectric dynamic theory and Lagrange’s equation, the coupled vibration equations of piezoelectric-propeller blades system under complex excitation are established. Applying MATLAB simulation method, the dynamic responses of the coupled blades under external and piezoelectric excitation are investigated. With finite-element method software, the correctness of the theoretical analysis is verified. Results show that the maximum amplitudes of the propeller blades are distributed at the end of the blades, thus placing the piezoelectric layers at the terminal blades can minimize the vibration of the propeller blades. Meanwhile, the vibration amplitudes of propeller blades can be reduced by more than 70% by applying piezoelectric coating. These results can be used to reduce the vibration and improve the dynamic performance during the unmanned underwater vehicle operating.

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