Stability and Drag Analysis of Wheeled Amphibious Vehicle Using CFD and Model Testing Techniques

2014 ◽  
Vol 592-594 ◽  
pp. 1210-1219 ◽  
Author(s):  
R. R. More ◽  
Piyush Adhav ◽  
K. Senthilkumar ◽  
M.W. Trikande
Keyword(s):  
Cfd Simulation ◽  
Scale Model ◽  
Cfd Analysis ◽  
Scaled Model ◽  
Towing Tank ◽  
Weapon Systems ◽  
Viable Solution ◽  
Present Generation ◽  
Combat Vehicle ◽  
Gross Vehicle Weight

Amphibious design of combat vehicle has become a challenging task in the context of increase in Gross Vehicle weight (GVW) of present generation combat vehicles due to demand for high protection levels and higher capacity engine and transmission, incorporation of multiple weapon systems, increased ammunition storage and larger addition of electrical and electronic items. Development of combat vehicles is complex and very expensive, and normally limited with less number of prototypes. The scale modeling and CFD analysis offers a viable solution to accomplish the amphibian design of a combat vehicle with adequate confidence before manufacturing the actual prototype. In the present work, an approach involving experimental towing test using scaled model and CFD simulation has been used to carry out the amphibious design of an 8X8, wheeled, combat vehicle with GVW of 22 ton. In this work, a 1/5thscaled model of the vehicle was manufactured and tested in the towing tank at different test speeds for drag and stability analysis. CFD analysis was carried out on the full scale model to gain adequate details about the dynamics of vehicle in the water in addition to drag estimation. Good correlation has been found in drag values and the flow patterns obtained from towing tank tests and CFD simulations.

Validation of mathematical model of electrothermal calculation of DC catenary on the basis of scale model

2018 ◽  
Vol 77 (4) ◽  
pp. 222-229 ◽  
Author(s):  
A. V. Paranin ◽  
A. B. Batrashov
Keyword(s):  
Mathematical Model ◽  
Operating Conditions ◽  
Scale Model ◽  
Contact Network ◽  
Scaled Model ◽  
Cross Sectional ◽  
Current Collection ◽  
Topological Features ◽  
Study Results ◽  
Real Physical Process

The article compares the results of calculation of the finite element simulation of current and temperature distribution in the scale model of the DC catenary with the data of laboratory tests. Researches were carried on various versions of the structural design of catenary model, reflecting the topological features of the wire connection, characteristic of the DC contact network. The proportions of the cross-sectional area of the scaled model wires are comparable to each other with the corresponding values for real DC catenary. The article deals with the operating conditions of the catenary model in the modes of transit and current collection. When studying the operation of the scale catenary model in the transit mode, the effect of the structural elements on the current distribution and heating of the wires was obtained. Within the framework of the scale model, theoretical assumptions about the current overload of the supporting cable near the middle anchoring have been confirmed. In the current collection mode, the experimental dependences of the current in the transverse wires of the scale model are obtained from the coordinate of the current collection point. Using the model it was experimentally confirmed that in the section of the contact wire with local wear, not only the temperature rise occurs but also the current redistribution due to the smaller cross section. Thus, the current share in other longitudinal wires of the scale model increases and their temperature rises. Scale and mathematical models are constructed with allowance for laboratory clamps and supporting elements that participate in the removal of heat from the investigated wires. Obtained study results of the scale model allow to draw a conclusion about the adequacy of the mathematical model and its correspondence to the real physical process. These conclusions indicate the possibility of applying mathematical model for calculating real catenary, taking into account the uneven contact wear wire and the armature of the contact network.

Abstract P531: Cerebral Blood Flow Analysis Using Flow Wire Measurements and CFD Analysis

Stroke ◽  
2021 ◽  
Vol 52 (Suppl_1) ◽  
Author(s):  
Aichi Chien ◽  
Huy Dinh ◽  
Viktor Szeder ◽  
Fernando Vinuela
Keyword(s):  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Flow Velocity ◽  
Cfd Simulation ◽  
Cfd Analysis ◽  
Flow Data ◽  
Velocity Data ◽  
Mean Flow ◽  
Good Agreement ◽  
Cerebral Vascular

Introduction: Clinical reports show that cerebral blood flow conditions are indicative of cerebral vascular disease. While methods for characterizing cerebral vascular flow have been extensively reported in the past, comparative analyses between direct flow measurements (DM) and computational flow dynamic (CFD) analysis remain limited. We hypothesize that flow data can be reliably measured both directly and through CFD in normal vessels. Methods: A left heart replicator was used as a realistic cardiac pump which maintained systolic pressure at 120 mmHg and diastolic pressure at 80 mmHg. A stenotic model with 50% stenosis for the ICA was connected to the replicator. A ComboWire was used for DM and recorded flow pressure and velocity. CFD was used to study flow. Results: In areas at the proximal end of the stenosis, the pressure and flow velocity derived from DM and CFD were in good agreement. At the end of systole and diastole, DM pressure were 145.42 mmHg and 73.53 mmHg, respectively. CFD simulation for the same system obtained the pressure at the end of systole and diastole of 147.16 mmHg and 74.64 mmHg, respectively. The velocity data collected from DM was at 15.40 cm/s and 7.74 cm/s for systolic flow and mean flow velocity. CFD measured flow was 17.85 cm/s and 11.37 cm/s, respectively. In areas at the distal end of the stenosis, pressure data showed good agreement between DM and CFD analysis. The DM were 138 and 70.81 mmHg at the end of systole and diastole, respectively; CFD simulation yielded 145.95 and 74.51 mmHg, respectively. Variations in the velocity data were observed at this location (Fig, pink arrows). Conclusion: DM of pressure showed good agreement with CFD simulation in all areas of the vessel. DM of velocity using the flow wire were highly affected by location of the measurement. CFD analysis can provide more consistent flow data for flow information collection along the vasculature.

Spraying Experiments with a Model Stern Trawler

1998 ◽  
Vol 42 (04) ◽  
pp. 260-265 ◽  
Author(s):  
K. K. Chung ◽  
E. P. Lozowski ◽  
W. P. Zakrzewski ◽  
R. Gagnon ◽  
T. Thompson
Keyword(s):  
Statistical Analysis ◽  
Froude Number ◽  
Significant Wave Height ◽  
Flux Distribution ◽  
Full Scale ◽  
Scale Model ◽  
Spray Droplet ◽  
Towing Tank ◽  
Ship Speed ◽  
Longitudinal Distance

With a view to formulating vessel spraying and icing models, 22 spraying experiments were performed in the IMD/NRC towing tank using a 1:13 scale model of the stern trawler MT Zandberg. Neglecting the effect of wind drag on the spray droplet trajectories, an empirical spray flux equation for the scale Zandberg was derived, based on a statistical analysis of the spraying data. Using Froude number scaling, this model-scale equation was transformed into a full-scale spray flux equation. This spraying study shows that the total spray flux generated during ship/wave collisions depends on ship speed (Vs) and significant wave height (H1/3) according to V3⅓, H7⅓ while the spray flux distribution over the foredeck varies exponentially with longitudinal distance. Using this full-scale spray flux equation, a spray trajectory model, taking wind drag effects into account, was subsequently developed.

Dynamic Instability of a High-Speed Planing Boat Model

2000 ◽  
Vol 37 (03) ◽  
pp. 146-152
Author(s):  
Eric Thornhill ◽  
Brian Veitch ◽  
Neil Bose
Keyword(s):  
Dynamic Stability ◽  
High Speed ◽  
Research Council ◽  
Dynamic Instability ◽  
National Research Council ◽  
Scale Model ◽  
Clear Water ◽  
Towing Tank ◽  
Stability Limits ◽  
Resistance Tests

A series of bare-hull resistance and self-propulsion tests were carried out on a 1/8 scale model of a 11.8 m long, waterjet-propelled planing hull in the clear water towing tank at the National Research Council of Canada's Institute for Marine Dynamics. The bare-hull resistance tests, performed with the waterjet inlets closed, spanned a range of eight model velocities and nine ballast conditions consisting of three displacements each with three positions of the longitudinal center of gravity. The hull was then fitted with two model waterjet thrusters and tested over the same speeds and ballast conditions. Dynamic instability, or porpoising, was seen during certain high-speed tests. A discussion of this behavior and its relation to published dynamic stability limits is given.

Skin Friction Resistance of Ships

1957 ◽  
Vol 1 (03) ◽  
pp. 3-12
Author(s):  
F. H. Todd
Keyword(s):  
Skin Friction ◽  
Present Status ◽  
Comparative Studies ◽  
Scale Model ◽  
Small Scale ◽  
Model Data ◽  
Towing Tank ◽  
Friction Resistance ◽  
Small Scale Model

The International Towing Tank Conference (ITTC) is to hold its 8th meeting in Madrid in September of this year. One of the subjects to be discussed will be the perennial one of how to estimate the resistance of a ship from that measured on a small-scale model in a towing tank. The Skin Friction Committee of the Conference was charged at the last meeting in Scandinavia in 1954, with reviewing the available data and making recommendations to the Conference in Madrid which will, it is hoped, be universally acceptable. Such a decision would remove one of the principal difficulties experienced in the use of model data in comparative studies. It is believed that a review of the present status of our knowledge in this field may be of interest to the members of the Society at this time.

CFD Analysis on Similarity Criteria of Hydrodynamic Characteristics for Gravity-Installed Anchors

2019 ◽  
Author(s):  
Jiancai Gao ◽  
Haixiao Liu
Keyword(s):  
Model Testing ◽  
Model Tests ◽  
Similarity Criteria ◽  
Scale Model ◽  
Hydrodynamic Characteristics ◽  
Cfd Analysis ◽  
Cfd Simulations ◽  
Tests Of Gravity ◽  
Free Falling ◽  
Reduced Scale

Abstract For reduced-scale model tests of gravity-installed anchors (GIAs), it is of great significance to extrapolate the testing results to prototype. This highlights the necessity of investigation of similarity criteria. The present work aims to find the similarity criteria of three prioritized hydrodynamic characteristics including VT, HP, and Cd for GIAs during installation in water through CFD simulations. In the present study, free falling processes of different reduced-scale T98 anchor models and prototype anchor is simulated, from which VT, HP, and Cd are extracted and analyzed to get the fitting curves for these three characteristics over reduced-scale λ. Based on these curves, hydrodynamic characteristics for prototype and other reduced-scale model can be extrapolated from model testing results. And, the researching procedure in this paper sets an example and reference to study about similarity criteria for other hydrodynamic characteristics.

scholarly journals CFD analysis of the ventilation heating system

2019 ◽  
Vol 20 (7) ◽  
pp. 708
Author(s):  
Miroslav Rimár ◽  
Andrii Kulikov ◽  
Marcel Fedak ◽  
Milan Abraham
Keyword(s):  
Heat Balance ◽  
Cfd Simulation ◽  
Heating System ◽  
Cfd Analysis ◽  
Ansys Fluent ◽  
Closed Area ◽  
Building Ventilation ◽  
Passive Houses ◽  
Air Circulation ◽  
The Heat Balance

Air conditioning is a significant part of the contemporary life. A lot of the medical papers confirmed the influence of the thermal comfort to the operability. The aim of the article is to understand the system of the building ventilation with the HRV unit. For this purpose, the CFD simulation model was elaborated. The ANSYS Fluent allows to calculate the heat balance of the room with secondary thermal gains like computers, monitors and humans. The results of the simulation approved that in the modern thermal passive houses heat balance calculations should take into account secondary thermal gains from the installed equipment. Also the air circulation in the closed area and the influence of the different barriers installed in the laboratory were investigated.

Optimal Hardware Placement in a Minitower Computer Enclosure System

2011 ◽  
Author(s):  
M. Alfaro Cano ◽  
A. Hernandez-Guerrero ◽  
C. Rubio Arana ◽  
Aristotel Popescu
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Cfd Simulation ◽  
Operating Temperature ◽  
Optimal Placement ◽  
Cfd Analysis ◽  
Computational Fluid Dynamics Cfd ◽  
Simulation Results ◽  
The Relationship ◽  
Key Questions

One of the requirements for existing personal computers, PCs, is that the hardware inside must maintain an operating temperature as low as possible. One way to achieve that is to place the hardware components at locations with enough airflow around it. However, the relationship between the airflow and temperature of the components is unknown before they are placed at specific locations inside a PC. In this work a Computational Fluid Dynamics (CFD) analysis is coupled to a Design of Experiment (DOE) methodology to answer typical minitower key questions: a) how do the possible positions of hardware components affect their temperature?, and b) is it possible to get an optimal placement for these hardware components using the data collected by the CFD simulation results? The DOE methodology is used to optimize the analysis for a very large number of possible configurations. The results help in identifying where the efforts need to be placed in order to optimize the positioning of the hardware components for similar configurations at the designing stage. Somehow the results show that general conclusions could be drawn, but that there are not specific rules that could be applied to every configuration.

Flow Behaviour Analysis of Injection Mixer for CNG Engines using Computational Fluid Dynamics

2018 ◽  
Vol 9 (5) ◽  
Author(s):  
R. Paullinga Prakash ◽  
S. Palani ◽  
D. Vijaya Kumar ◽  
S. Arun Kumar ◽  
S. Shanmugan
Keyword(s):  
Fluid Dynamics ◽  
Cfd Simulation ◽  
Three Dimensional ◽  
Fuel Mixture ◽  
Flow Behaviour ◽  
Liquid Fuels ◽  
Cfd Analysis ◽  
Design Modification ◽  
Gaseous Fuels ◽  
Fuel Tube

Use of gaseous fuels for fuelling the engines reduces reactive hydrocarbons and do not pose the problem of vaporization as with the liquid fuels. One of the problems of gaseous mixers is the ability to prepare a homogeneous mixing of air and fuel at a specific air-fuel ratio prior to entering the engine resulting high exhaust emissions. The objective of this project is to carry out three dimensional CFD analysis of CNG injection mixer to understand the flow behaviour of air fuel mixture and to optimize the design of injection mixer. The analysis was carried out by varying the injection position and injection inclination. The results of the CFD simulation could be used to understand the effect of position of fuel tube, injection inclination in the mixing of air and fuel. Further the results of the study would also be considered for the design modification.

Forced Oscillation Model Tests for Determination of Hydrodynamic Coefficients of Large Subsea Blowout Preventers

2015 ◽  
Author(s):  
Xavier Arino ◽  
Jaap de Wilde ◽  
Massimiliano Russo ◽  
Guttorm Grytøyr ◽  
Michael Tognarelli
Keyword(s):  
Large Scale ◽  
Forced Oscillation ◽  
Model Tests ◽  
Scale Model ◽  
Hydrodynamic Coefficients ◽  
Lumped Mass ◽  
Towing Tank ◽  
Steady Current ◽  
Large Scale Model

Large scale model tests have been conducted in a towing tank facility for the determination of the hydrodynamic coefficients of subsea blowout preventers. A subsea blowout preventer (BOP) is a large, complex device 10–15 [m] tall, weighing 200–450 [ton]. The BOP stack consists of two assemblies, the ‘lower marine riser package’ (LMRP) connected to the riser string and the BOP itself, connected to the wellhead. Together they represent a large lumped mass, which directly influences the natural frequencies and vibration modes of the riser system, particularly those of the BOP-wellhead-casing assembly. Large uncertainties in the estimates of the hydrodynamic coefficients (added mass, lift and drag or damping) result in large uncertainties in the fatigue damage predictions of the riser and wellhead system. The trend toward larger and heavier BOPs, which could place BOP-wellhead-casing oscillation frequencies in the range of wave frequencies, has motivated Statoil and BP to start a new research project on this subject. The project involves a large scale model test for experimental determination of hydrodynamic coefficients. Two different BOP designs were tested in a towing tank at model scale 1:12. The models weighed about 50 [kg] in air and were about 1.2–1.5 [m] tall. A six-degree-of-freedom oscillator was mounted under the carriage of the towing tank for oscillation of the models in different directions. Static tow tests and forced oscillation tests with and in the absence of steady current were carried out. Keulegan-Carpenter (KC) numbers ranged between 0.2 and 2.0, while the Sarpkaya frequency parameter β was in the range from 4,000 to 50,000. The Reynolds numbers of the static tow tests ranged between 50,000 and 150,000. This paper focuses particularly on tests in the surge direction with and in the absence of a steady current. Results indicate that the hydrodynamic coefficients for BOP stacks are quite different from those of simpler geometries like a circular cylinder. In addition, they provide new insight for analytical modeling of global hydrodynamic forces on BOPs in many configurations and scenarios.

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