scholarly journals On Application of Prandtl-Obukhov Formula in the Numerical Model of the Turbulent Layer Depth Dynamics

2020 ◽  
pp. 37-47
Author(s):  
Victor M. Belolipetskii ◽  
Svetlana N. Genova
Keyword(s):  
Experimental Data ◽  
Numerical Simulation ◽  
Numerical Model ◽  
Tangential Stress ◽  
Stratified Fluid ◽  
Turbulent Exchange ◽  
Layer Depth ◽  
Turbulent Layer

A numerical simulation of the penetration of the turbulent layer in a stably stratified fluid under the action of tangential stress was performed. For the coefficient of vertical turbulent exchange, the Prandtl–Obukhov formula is used. The results of the calculations are consistent with known experimental data and calculations by other authors

Numerical Simulation of Twin-Parachute Inflation Process for Aircraft Ejection Escape

2020 ◽  
Author(s):  
Liwu Wang ◽  
Mingzhang Tang ◽  
Sijun Zhang
Keyword(s):  
Experimental Data ◽  
Numerical Simulation ◽  
Numerical Model ◽  
Physical Models ◽  
The Other ◽  
Arbitrary Lagrangian Eulerian ◽  
Safe Distance ◽  
Structure Interaction ◽  
Parachute Inflation ◽  
Good Agreement

Abstract In order to study the safe distance between twin-parachute during their inflation process for fighter ejection escape, the fighter was equipped with two canopies and two seats, two types of parachute were used to numerically simulate their inflation process, respectively. One of them is C-9, the other a slot-parachute (S-P). Their physical models were built, then the meshes inside and around both parachutes were generated for fluid-structure interaction (FSI) simulation. The penalty function and the arbitrary Lagrangian-Eulerian (ALE) method were employed in the FSI simulation. To validate the numerical model for FSI simulation, at first the single parachute of the twin-parachute was used for the FSI simulation, the predicted inflation times for both types of parachute were compared with the experimental data. The computed results are in good agreement with experimental data. As a result, the inflation times were predicted with twin-parachute for both kinds of parachute. On the basis of the locations of ejected seats after the separation of seat and pilot, the initial locations and orientations of twin-parachute were also obtained. The numerical simulations for both kinds of parachute were performed by the FSI method, respectively. Our results illustrate that when the interval time for two seats ejected is greater than 0.25s, two pilots attached the twin-parachute are safe, and the twin-parachute would not interfere each other. Moreover, our results also indicate that the FSI simulation for twin-parachute inflation process is feasible for engineering applications and have a great potential for wide use.

Modeling Support Loss in SOI-Based Micromechanical Resonators

2007 ◽  
Author(s):  
Yang Xu ◽  
Zhili Hao
Keyword(s):  
Experimental Data ◽  
Numerical Simulation ◽  
Numerical Model ◽  
Infinite Medium ◽  
Silicon On Insulator ◽  
Combined Model ◽  
Vibration Displacement ◽  
Micromechanical Resonators ◽  
Time Harmonic ◽  
Quality Factor Q

In light of recent efforts to quantitatively evaluate the quality factor (Q) of micromechanical resonators, this paper presents an analytical-numerical model for calculating support loss in micromechanical resonators made from Silicon-On-Insulator (SOI) wafers. The time-harmonic stress due to the vibrations in a micromechanical resonator is obtained through numerical simulation, while the vibration displacement on substrate due to the stress from micromechanical resonators is analytically derived, with the assumption that the substrate is a semi-infinite medium. The combination of the time-harmonic stress from the resonator and the vibration displacement on substrate gives rise to a quantitative evaluation of support loss, which is further verified with the experimental data in the literature. This analytical-numerical combined model is general and applicable to SOI-based micromechanical resonators with different structural geometries.

scholarly journals Application of CFD to the Design of Multirun Meter Station With Ultrasonic Meters

1998 ◽  
Author(s):  
Jaroslaw Jelen ◽  
Wojciech Studzinski ◽  
Michael Brown
Keyword(s):  
Fluid Dynamics ◽  
Experimental Data ◽  
Numerical Simulation ◽  
Numerical Model ◽  
Experimental Information ◽  
Out Of Plane ◽  
Ultrasonic Flow Meter ◽  
Computational Fluid Dynamics Cfd ◽  
Good Agreement ◽  
Subsequent Integration

Designers of ultrasonic meter stations with headers do not have any experimental data which can help to determine proper location of the multipath ultrasonic meter within the meter run. The results of meter tests are limited to such configurations as a single 90° elbows and two elbows out of plane. Because of the variety of header layouts used in practice any experimental information related to this piping configuration will be of limited use in the design process. The proposed approach is based on the application of Computational Fluid Dynamics (CFD) methods to the evaluation of header effects on ultrasonic flow meter using a commercial CFD code combined with a numerical model of the ultrasonic meter. The numerical simulation of the flow field in the header and meter runs and subsequent integration of the obtained velocity field in a numerical model of multipath ultrasonic meter were used to determine the optimal meter position. This approach was validated against available experimental data on the ultrasonic meter performance downstream of single and double elbow. The comparison of simulations and test data has shown very good agreement of trends exhibited by the meter. The trends were replicated by the simulator within approximately 1% for X/D ≥5 and within 0.5% for X/D ≥9.

Comparative Study of Drill Pipe Erosion Wear in Gas Drilling and Mud Drilling

2010 ◽  
Vol 34-35 ◽  
pp. 1708-1712 ◽  
Author(s):  
Xiao Hua Zhu ◽  
Shao Hu Liu ◽  
Hua Tong
Keyword(s):  
Experimental Data ◽  
Numerical Simulation ◽  
Numerical Model ◽  
Comparative Study ◽  
Field Condition ◽  
Erosion Rate ◽  
Drill Pipe ◽  
Erosion Wear ◽  
Gas Drilling ◽  
Local Erosion

Failure of drill pipe is very severe in gas drilling. Based on the erosion theory and field condition, the erosion of drill pipe is investigated by using numerical simulation. The agreement between the simulation result and experimental data is very good, this agreement indicates that the numerical model is realistic in this paper. The erosion wear of drill pipe is investigated in gas drilling and mud drilling by using this model. According to study result of drill pipe erosion between gas drilling and mud drilling, the erosion rate of drill pipe in gas drilling is greater than that of in mud drilling. The result shows that the local erosion rate of joint is more severe than that of the drill pipe body in gas drilling, and also the local erosion of drill pipe body is severe. There are many eroded pits on drill pipe body in gas drilling. This study will reveal the failure mechanism of drill pipe in gas drilling, and also have some guiding significance to reduce the failure of drill pipe.

Combined Experimental and Numerical Study for Multiple Microchannel Heat Transfer System

2010 ◽  
Author(s):  
Jingru Zhang ◽  
Yogesh Jaluria ◽  
Tiantian Zhang ◽  
Li Jia
Keyword(s):  
Experimental Data ◽  
Numerical Simulation ◽  
Steady State ◽  
Numerical Model ◽  
Initial Conditions ◽  
Numerical Study ◽  
Numerical Models ◽  
Three Dimensional ◽  
Variation Versus ◽  
Heat Transfer System

Multiple microchannel heat sinks for potential use for electronic chip cooling are studied experimentally and numerically to characterize their thermal performance. The numerical simulation is driven by experimental data, which are obtained concurrently, to obtain realistic, accurate and validated numerical models. The ultimate goal is to design and optimize thermal systems. The experimental setup was established and liquid flow in the multiple microchannels was studied under different flow rates and heat influx. The temperature variation versus time was recorded by thermocouples, from which the time needed to reach steady state was determined. Temperature variations under steady state conditions were compared with three-dimensional steady state numerical simulation for the same boundary and initial conditions. The experimental data served as input parameters for the validation of the numerical model. In case of discrepancy, the numerical model was improved. A fairly good agreement between the experimental and simulation results was obtained. The numerical model also served to provide input that could be employed to improve and modify the experimental arrangement.

Numerical Simulation of Dynamic Positioning in Ice

2013 ◽  
Vol 47 (2) ◽  
pp. 14-30 ◽  
Author(s):  
Ivan Metrikin ◽  
Sveinung Løset ◽  
Nils Albert Jenssen ◽  
Sofien Kerkeni
Keyword(s):  
Experimental Data ◽  
Numerical Simulation ◽  
Numerical Model ◽  
Element Model ◽  
Future Research ◽  
Data Series ◽  
Dynamic Positioning ◽  
Ice Drift ◽  
Simulation Results

AbstractNumerical simulation of dynamic positioning (DP) in ice is a novel research topic that has potential in many industrial and scientific applications. This paper reviews some challenges associated with numerical ice modeling and presents a classification of approaches for modeling the ice loads in DP simulations. The approaches are classified into three groups: empirical and statistical models, experimental data series methods, and physically based modeling. The strengths and weaknesses of the approaches are summarized, and recommended uses are outlined in this paper. In addition, a novel, nonsmooth, discrete element model of a DP vessel in managed ice is presented. The model was used to perform a numerical multibody simulation of a series of model tests with a conceptual Arctic drillship on DP in managed ice using the commercial physics engine Vortex. The numerical model simulated the ice basin, the DP vessel, the managed ice, the surrounding fluid, and their interactions. Comparison of the simulation results with experimental data showed that for head-on ice drift, the numerical model reproduced the experimental results reasonably well. However, for higher ice drift angles, discrepancies between the simulation results and the model testing data increased considerably. Possible reasons for the discrepancies are discussed in the paper, along with suggestions for future research. To the best of the authors’ knowledge, both the classification of various approaches for simulating DP in ice and the high-fidelity numerical DP model are novel and have not been published previously.

scholarly journals Blowing and drifting snow in Alpine terrain: numerical simulation and related field measurements

1998 ◽  
Vol 26 ◽  
pp. 174-178 ◽  
Author(s):  
Peter Gauer
Keyword(s):  
Numerical Simulation ◽  
Numerical Model ◽  
Three Dimensional ◽  
Field Measurements ◽  
Blowing Snow ◽  
Related Field ◽  
Drifting Snow ◽  
Physically Based ◽  
Snow Transport

A physically based numerical model of drifting and blowing snow in three-dimensional terrain is developed. The model includes snow transport by saltation and suspension. As an example, a numerical simulation for an Alpine ridge is presented and compared with field measurements.

scholarly journals Investigation of the Thickness Differential on the Formability of Aluminum Tailor Welded Blanks

Metals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 875
Author(s):  
Jie Wu ◽  
Yuri Hovanski ◽  
Michael Miles
Keyword(s):  
Experimental Data ◽  
Finite Element ◽  
Numerical Model ◽  
Plastic Strain ◽  
Finite Element Model ◽  
Equivalent Plastic Strain ◽  
Element Model ◽  
Dome Height ◽  
Tailor Welded Blanks ◽  
Simulation Results

A finite element model is proposed to investigate the effect of thickness differential on Limiting Dome Height (LDH) testing of aluminum tailor-welded blanks. The numerical model is validated via comparison of the equivalent plastic strain and displacement distribution between the simulation results and the experimental data. The normalized equivalent plastic strain and normalized LDH values are proposed as a means of quantifying the influence of thickness differential for a variety of different ratios. Increasing thickness differential was found to decrease the normalized equivalent plastic strain and normalized LDH values, this providing an evaluation of blank formability.

scholarly journals Fibre-induced drag reduction

2008 ◽  
Vol 602 ◽  
pp. 209-218 ◽  
Author(s):  
J. J. J. GILLISSEN ◽  
B. J. BOERSMA ◽  
P. H. MORTENSEN ◽  
H. I. ANDERSSON
Keyword(s):  
Experimental Data ◽  
Numerical Simulation ◽  
Reynolds Number ◽  
Drag Reduction ◽  
Elastic Layer ◽  
Turbulent Drag Reduction ◽  
Rigid Polymer ◽  
Fibre Concentration ◽  
Induced Drag ◽  
Turbulent Drag

We use direct numerical simulation to study turbulent drag reduction by rigid polymer additives, referred to as fibres. The simulations agree with experimental data from the literature in terms of friction factor dependence on Reynolds number and fibre concentration. An expression for drag reduction is derived by adopting the concept of the elastic layer.

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