INVESTIGATION OF UNDERWATER MOTION PARAMETERS FOR INERT CONICAL MODELS

2021 ◽  
pp. 78-89
Author(s):  
A.N. Ishchenko ◽  
◽  
V.V. Burkin ◽  
A.S. D’yachkovskiy ◽  
A.V. Chupashev ◽  
...  
Keyword(s):  
Flow Regime ◽  
High Speed ◽  
Computational Method ◽  
Velocity Variation ◽  
Model Parameters ◽  
First Approximation ◽  
Supercavitating Flow ◽  
Flat Disk ◽  
Extended Range ◽  
Positive Effect

This paper considers high-speed underwater motion of an axisymmetric inert conical model in a supercavitation flow regime. Experimental data on the model velocity variation with distance in water are obtained. Based on these data, a computational method, which is developed to determine the model velocity, is validated. A comparison of the calculated and experimental results obtained in a hydroballistic track shows that, in the first approximation, the motion of the model in a supercavitating flow regime can be considered as the motion of a flat disk having a mass and being streamed around at the developed cavitation directed normally to the surface. Experimental contours of supercaverns are compared with those calculated using the known computational methodology. The conditions ensuring supercavitation motion of the inert conical models in water are determined. As a result, the extended range of the horizontal motion is calculated for the inert conical models moving in a supercavitation regime under water at a depth up to 200 m at given initial velocity, depth of the trajectory location, and model parameters. It is found that reducing of a cavitator radius does not always have a positive effect on the range of the inert model motion.

scholarly journals A faster escape does not enhance survival in zebrafish larvae

2017 ◽  
Vol 284 (1852) ◽  
pp. 20170359 ◽  
Author(s):  
Arjun Nair ◽  
Christy Nguyen ◽  
Matthew J. McHenry
Keyword(s):  
High Speed ◽  
Larval Fish ◽  
Body Position ◽  
Three Dimensional ◽  
Limited Range ◽  
The Body ◽  
Model Parameters ◽  
Fish Prey ◽  
Zebrafish Larvae ◽  
Fish Predators

An escape response is a rapid manoeuvre used by prey to evade predators. Performing this manoeuvre at greater speed, in a favourable direction, or from a longer distance have been hypothesized to enhance the survival of prey, but these ideas are difficult to test experimentally. We examined how prey survival depends on escape kinematics through a novel combination of experimentation and mathematical modelling. This approach focused on zebrafish ( Danio rerio ) larvae under predation by adults and juveniles of the same species. High-speed three-dimensional kinematics were used to track the body position of prey and predator and to determine the probability of behavioural actions by both fish. These measurements provided the basis for an agent-based probabilistic model that simulated the trajectories of the animals. Predictions of survivorship by this model were found by Monte Carlo simulations to agree with our observations and we examined how these predictions varied by changing individual model parameters. Contrary to expectation, we found that survival may not be improved by increasing the speed or altering the direction of the escape. Rather, zebrafish larvae operate with sufficiently high locomotor performance due to the relatively slow approach and limited range of suction feeding by fish predators. We did find that survival was enhanced when prey responded from a greater distance. This is an ability that depends on the capacity of the visual and lateral line systems to detect a looming threat. Therefore, performance in sensing, and not locomotion, is decisive for improving the survival of larval fish prey. These results offer a framework for understanding the evolution of predator–prey strategy that may inform prey survival in a broad diversity of animals.

Inverse Dynamic Analysis and Linearisation of a High Speed Parallel Mechanism

2005 ◽  
Author(s):  
M. Necip Sahinkaya ◽  
Yanzhi Li
Keyword(s):  
Dynamic Analysis ◽  
Parallel Mechanism ◽  
High Speed ◽  
Inverse Dynamics ◽  
Motion Path ◽  
Model Parameters ◽  
Control Input ◽  
Inverse Dynamic ◽  
Inverse Dynamic Analysis ◽  
Dynamics Models

Inverse dynamic analysis of a three degree of freedom parallel mechanism driven by three electrical motors is carried out to study the effect of motion speed on the system dynamics and control input requirements. Availability of inverse dynamics models offer many advantages, but controllers based on real-time inverse dynamic simulations are not practical for many applications due to computational limitations. An off-line linearisation of system and error dynamics based on the inverse dynamic analysis is developed. It is shown that accurate linear models can be obtained even at high motion speeds eliminating the need to use computationally intensive inverse dynamics models. A point-to-point motion path for the mechanism platform is formulated by using a third order exponential function. It is shown that the linearised model parameters vary significantly at high motion speeds, hence it is necessary to use adaptive controllers for high performance.

A Validation Study of the Mixed-Foil Concept for High-Speed Hydrofoils

1976 ◽  
Vol 20 (02) ◽  
pp. 85-94
Author(s):  
D. P. Wang ◽  
Young T. Shen
Keyword(s):  
Validation Study ◽  
High Speed ◽  
High Speeds ◽  
Supercavitating Flow ◽  
The Future

A hydrodynamic validation study of the concept of the mixed foil has been conducted. A mixed foil is a streamlined hydrofoil equipped with a flap or other device which, above a certain speed, can be activated so as to change the flow around the foil into a supercavitating flow. At take-off and at moderate speeds, a mixed foil is operated as a subcavitating foil; at high speeds, it is operated as a supercavitating foil. During high-speed operations, a reduction in the wetted planform area of a mixed foil is proposed. The present study produces a design outline for the mixed foil and identifies essential problems which should be studied in the future. The analysis is illustrated by using hydrofoils with plano-convex sections. The lift-to-drag ratios at takeoff and at 45-knot and 83-knot cruising speeds are obtained.

Mechanics of the influx phase in the jet regurgitant mode of a powered resonance tube

2019 ◽  
Vol 18 (2-3) ◽  
pp. 279-298 ◽  
Author(s):  
Bhavraj Thethy ◽  
David Tairych ◽  
Daniel Edgington-Mitchell
Keyword(s):  
Shock Wave ◽  
High Speed ◽  
Fluid Velocity ◽  
Velocity Variation ◽  
Shock Strength ◽  
Velocity Change ◽  
Resonator Length ◽  
Time Resolved ◽  
Reflected Waves ◽  
Shock Position

Time-resolved visualisation of shock wave motion within a powered resonant tube (PRT) is presented for the regurgitant mode of operation. Shock position and velocity are measured as functions of both time and space from ultra-high-speed schlieren visualisations. The shock wave velocity is seen to vary across the resonator length for both the incident and reflected waves. Three mechanisms are explored as explanations for the variation in velocity: change in local fluid velocity, variation in shock strength and variations in local temperature. For the incident wave, local fluid velocity and shock strength are extracted from the data and both are demonstrated to contribute to the observed variation, with a non-trivial remainder likely explained by variation in temperature.

scholarly journals Deformation heterogeneity and texture in surface severe plastic deformation of copper

2016 ◽  
Vol 472 (2187) ◽  
pp. 20150486 ◽  
Author(s):  
Saurabh Basu ◽  
Zhiyu Wang ◽  
Christopher Saldana
Keyword(s):  
Plastic Deformation ◽  
Severe Plastic Deformation ◽  
High Speed ◽  
Surface Deformation ◽  
Image Correlation ◽  
Surface Mechanical Attrition Treatment ◽  
Model Parameters ◽  
Texture Model ◽  
Mechanical Attrition ◽  
Deformation Mechanics

Comprehensive understanding of thermomechanical response and microstructure evolution during surface severe plastic deformation (S 2 PD) is important towards establishing controllable processing frameworks. In this study, the evolution of crystallographic textures during directional surface mechanical attrition treatment on copper was studied and modelled using the visco-plastic self-consistent framework. In situ high-speed imaging and digital image correlation of surface deformation in circular indentation were employed to elucidate mechanics occurring in a unit process deformation and to calibrate texture model parameters. Material response during directional surface mechanical attrition was simulated using a finite-element model coupled with the calibrated texture model. The crystallographic textures developed during S 2 PD were observed to be similar to those resultant from uniaxial compression. The implications of these results towards facilitating a processing-based framework to predict deformation mechanics and resulting crystallographic texture in S 2 PD configurations are briefly discussed.

scholarly journals Computational Test Design for High-Speed Liquid Impact and Dispersal

2011 ◽  
Author(s):  
Alexander L. Brown ◽  
Kurt E. Metzinger
Keyword(s):  
High Speed ◽  
Water Channel ◽  
Computational Method ◽  
Computational Fluid Mechanics ◽  
Reacting Flow ◽  
Validation Data ◽  
Sled Test ◽  
The Impact ◽  
Scale Data ◽  
Limited Scope

Transportation accidents frequently involve liquids dispersing in the atmosphere. An example is that of aircraft impacts, which often result in spreading fuel and a subsequent fire. Predicting the resulting environment is of interest for design, safety, and forensic applications. This environment is challenging for many reasons, one among them being the disparate time and length scales that must be resolved for an accurate physical representation of the problem. A recent computational method appropriate for this class of problems has been developed for modeling the impact and subsequent liquid spread. This involves coupling a structural dynamics code to a turbulent computational fluid mechanics reacting flow code. Because the environment intended to be simulated with this capability is difficult to instrument and costly to test, the existing validation data are of limited scope, relevance, and quality. A rocket sled test is being performed where a scoop moving through a water channel is being used to brake a pusher sled. We plan to instrument this test to provide appropriate scale data for validating the new modeling capability. The intent is to get high fidelity data on the break-up and evaporation of the water that is ejected from the channel as the sled is braking. These two elements are critical to fireball formation for this type of event involving fuel in the place of water. We demonstrate our capability in this paper by describing the pre-test predictions which are used to locate instrumentation for the actual test. We also present a sensitivity analysis to understand the implications of length scale assumptions on the prediction results.

Design of a Scaled Model for a High Rise, High Speed Elevator

2001 ◽  
Author(s):  
W. D. Zhu ◽  
L. J. Teppo
Keyword(s):  
High Speed ◽  
Scaling Laws ◽  
Sufficient Accuracy ◽  
Model Parameters ◽  
Minimal Effect ◽  
Model Design ◽  
Scaled Model ◽  
Lateral Dynamics ◽  
High Rise ◽  
Dimensionless Groups

Abstract A novel scaled model is developed to simulate the linear lateral dynamics of a hoist cable with variable length in a high rise, high speed elevator. The dimensionless groups used to formulate the scaling laws are derived through dimensional analysis. The model parameters are selected based on the scaling laws subject to space and hardware constraints. It is demonstrated that while it is almost impossible to obtain a fully scaled model unless the model is extremely tall, a reasonably sized model can be constructed with sufficient accuracy. The scaling laws that are not satisfied can be rendered to have a minimal effect on the scaling between the model and prototype. In conjunction with the model design, an analysis of model tension in a closed cable loop is developed. A new movement profile, which ensures a continuous jerk function during the entire period of motion, is derived. Practical considerations that occur in the design of the model are addressed. The methodology can be used to investigate the vibration of a very long cable in other applications.

Spatio-Temporal Development of Supercavitation Over an Impulsively Launched Projectile

2006 ◽  
Author(s):  
C. J. Weiland ◽  
P. P. Vlachos
Keyword(s):  
High Speed ◽  
Temporal Development ◽  
Two Phase ◽  
Time Resolved ◽  
Gas Gun ◽  
Supercavitating Flow ◽  
Image Velocimetry ◽  
Spatio Temporal ◽  
Asymmetric Vortices ◽  
First Time

Supercavitation inception and formation was studied over blunt projectiles. The projectiles were fired using a gas gun method. In this method, projectiles are launched under the action of expanding detonation gases. Both qualitative and quantitative optical flow diagnostics using high speed digital imaging were used to analyze the spatio-temporal development of the supercavitating flow. For the first time, quantification of the supercavitation was achieved using Time Resolved Digital Particle Image Velocimetry (TRDPIV) detailing the two phase flow field surrounding the translating projectiles and the gas vapor bubble. Experimental results indicate that the supercavity forms at the aft end of the projectile and travels forward along the direction of projectile travel. The impulsive start of the projectile generates two asymmetric vortices which are shed from the blunt nose of the projectile. The vortices interact with the moving cavity and subsequently deform. This interaction is believed to directly contribute to the instabilities in the flight path.

Experimental Study on Flow Patterns and Pressure Drop of Decaying Swirling Gas-Liquid Flow in a Vertical Pipe

2020 ◽  
Author(s):  
Jiarong Zhang ◽  
Li Liu ◽  
Shuai Liu ◽  
Hanyang Gu
Keyword(s):  
Pressure Drop ◽  
Flow Regime ◽  
Liquid Flow ◽  
High Speed ◽  
Phase Distribution ◽  
Swirling Flow ◽  
Tangential Velocity ◽  
High Speed Camera ◽  
Vertical Pipe ◽  
Gas Liquid Flow

Abstract Vertical swirling gas-liquid flow is a kind of complex two-phase flow containing a nonzero tangential velocity component in engineering applications. The accurate flow regime characterization, phase distribution information and pressure drop data about vertical swirling flow are the basis for the optimization of steam generator (SG), which can greatly reduce the cost and improve the safety of nuclear plants. To get these key parameters of swirling vertical flow, we have made a comprehensive visualization experiment in a vertical pipe with 30mm diameter and 5m length by high-speed camera. The experimental pipe is separated into swirling part and non-swirling part. We have set three observation section with different vertical heights in the swirling part. Changing the flow rate of water and gas, different swirling flow pattern photos can be captured by high-speed camera. Based on the photos of different positions and image-processing MATLAB code, we can get three flow regime maps and figure out the decaying law of swirling gas-liquid flow. The pressure drop can be recorded by rotameter at each position. The decaying law of pressrure drop can be concluded from it. These data can be a guide for designing gas-liquid separator in SG to improve the efficiency of nuclear plant.

scholarly journals Cuttings Transport In Horizontal And Highly Deviated Wellbores

2011 ◽  
pp. 1-14 ◽  
Author(s):  
Ali Piroozian ◽  
Issham Ismail
Keyword(s):  
Flow Regime ◽  
Removal Efficiency ◽  
Drilling Fluid ◽  
Fluid Velocity ◽  
Fluid Viscosity ◽  
Flow Loop ◽  
Cuttings Transport ◽  
Drill Cuttings ◽  
Hole Cleaning ◽  
Positive Effect

Lencongan dari laluan tegak menyebabkan rincisan gerudi berkumpul pada bahagian bawah lubang telaga sehingga terbentuknya lapisan rincisan. Akibatnya, berlaku beberapa permasalahan operasi ketika berlangsungnya penggerudian. Daya seret dan kilas yang melampau, kesukaran yang dialami ketika penyorongan rentetan selongsong ke dalam lubang telaga, kesukaran untuk memperoleh operasi penyimenan yang baik, dan lekatan mekanikal paip gerudi adalah antara beberapa contoh lazim yang berkaitan dengan permasalahan terbabit. Sehubungan itu, pemahaman yang baik tentang parameter utama operasi yang mempengaruhi pembersihan lubang telaga adalah penting. Artikel ini mengetengahkan keputusan daripada kajian makmal yang telah dilaksanakan untuk menilai keberkesanan tiga jenis bendalir gerudi dalam menyingkir rincisan gerudi. Kajian makmal melibatkan penggunaan gelung legap aliran sepanjang 17 kaki dengan diameter 2 inci sebagai bahagian ujian. Bagi setiap uji kaji, prestasi pengangkutan rincisan (CTP - Cuttings Transport Performance) ditentukan menerusi pengukuran berat. Keputusan uji kaji dianalisis untuk memperoleh kesan menyeluruh ketiga-tiga parameter operasi, iaitu kelikatan bendalir gerudi, halaju bendalir, dan kecondongan lubang telaga. Kajian terkini membuktikan bahawa penggunaan bendalir gerudi berkelikatan tinggi berupaya meningkatkan CTP jika regim aliran adalah gelora. Walau bagaimanapun, peningkatan kelikatan dalam regim aliran peralihan atau laminar masing-masing mengurangkan CTP secara beransur atau mendadak. Kajian juga menunjukkan bahawa peningkatan sudut kecondongan dari 60° ke 90° memberikan kesan yang positif terhadap CTP. Parameter operasi yang memberikan kesan yang ketara dalam kajian ini ialah halaju aliran, dengan peningkatan kecil yang dialami oleh halaju aliran berjaya memberikan kesan positif yang nyata dalam pembersihan lubang telaga. Kata kunci: Kecekapan penyingkiran rincisan; prestasi pengangkutan rincisan; rincisan gerudi; bendalir gerudi; pembersihan lubang telaga Deviation from vertical path makes drill cuttings to accumulate on the lower side of the wellbore that induces the formation of cuttings bed. Subsequently, relative problems occur while drilling. Excessive torque and drag, difficulties in running casing in hole and accomplishing good cementing jobs and mechanical pipe sticking are few of the classical examples of such problems. Therefore, a comprehensive understanding of influential parameters on hole cleaning seems to be essential. This paper presents results of an experimental study that was carried out to evaluate cuttings removal efficiency of three types of drilling fluid. Experiments were conducted using a 17 feet long opaque flow loop of 2 inch diameter as test section. For each test, the amount of cuttings transport performance (CTP) was determined from weight measurements. Three operating parameters were considered, namely drilling fluid viscosity, fluid velocity, and hole inclination. It showed that the use of high-viscosity drilling fluid improved CTP if the flow regime was turbulent. However, increasing viscosity when flow regime was transient or laminar flow lessened CTP gradually or sharply respectively. It was also revealed that an incremental increase in hole inclination from 60° to 90° has a positive effect on CTP. The most influential parameter in this study was fluid velocity in which a small raise of fluid velocity resulted in a substantial positive effect on hole cleaning. Key words: Cuttings removal efficiency; cuttings transport performance; drill cuttings; drilling fluid; hole cleaning

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