The Simulation Research of Damping Characteristics for the Underwater Vehicle Moving under or Exceeding Water

2013 ◽  
Vol 432 ◽  
pp. 281-287
Author(s):  
Chun Fang Zhang ◽  
Jing Bo Gao ◽  
Hai Bo Lü ◽  
Zhen Jun Zhao ◽  
Cong Wang
Keyword(s):  
Numerical Simulation ◽  
Damping Ratio ◽  
Continuous Process ◽  
Underwater Vehicle ◽  
Water Model ◽  
Simulation Research ◽  
Fluid Structure ◽  
Damping Characteristics ◽  
The Impact ◽  
Water Exit

The vehicle may vibrate when it moves under or exceeding water. This vibration will interact with the flow filed around to form a fluid-structure interactiondynamics system. In this paper, the numerical simulation of a cylinder in the process of moving under or exceeding water with ABAQUS and FLUENT is presented. Simultaneously, the first three damping ratio of the system are obtained by damping identification. For different density, viscosity and velocity of water, model separately to get the impact of each factor. Besides, the continuous process of exceeding water has been discretized to obtaindifferent oscillating curvesat different positions with respect to the water,and then the change of the damping ratio is presented. Thus the damping characteristics of the system in the water-exit process have been obtained approximately.

scholarly journals Investigation on Damping Characteristics of Hydrostatic Bearing Film by Using Scale Method

2021 ◽  
Author(s):  
Sheng-Yen Hu ◽  
Wen-Chou Chen ◽  
Chien-Hsun Wang ◽  
Hsin-Ming Fu ◽  
Yuan Kang
Keyword(s):  
Damping Ratio ◽  
Resonant Peak ◽  
Test Results ◽  
Scaling Method ◽  
Single Degree Of Freedom ◽  
Hydrostatic Bearing ◽  
Damping Characteristics ◽  
Mass Spring ◽  
The Impact

Abstract The resonant peaks can be suppressed by damping, those effects is dependent on damping ratio of system. In this paper, we propose a scaling method to evaluate the damping ratio of hydrostatic bearings for the data from model test. This method fits specifically for the overdamping of all hydrostatic bearing. This is direct and the easiest method to obtain the damping characteristics of oil film for the lowest band before the first resonant peak. The frequency responses of acceleration per force for a single-degree-of-freedom mass-spring-damper model is used to generate the evaluation scales for the damping ratios of the modal test results of worktable mounting on hydrostatic bearing. The case study for experimental results of the impact response are evaluated for damping ratio of the hydrostatic film by these method. Furthermore, using this scaling method, the influences of three types of compensations on the damping ratio of a hydrostatic bearing are compared. The results reveal that the constant flow has the largest damping ratio, and the capillary restrictor has the smallest one.

Investigation of Granular Damping in Transient Vibrations Using Hilbert Transform Based Technique

2008 ◽  
Vol 130 (3) ◽  
Author(s):  
X. Fang ◽  
H. Luo ◽  
J. Tang
Keyword(s):  
Hilbert Transform ◽  
Damping Ratio ◽  
Temporal Frequency ◽  
Nonlinear Damping ◽  
Vibration Level ◽  
Damping Characteristics ◽  
The Difference ◽  
The Hilbert Transform ◽  
Granular Damping ◽  
The Impact

Granular damping results from a combination of energy dissipation mechanisms including the impact and the friction between the vibrating structure and granules and among the granules. Although simple in concept, granular damping is very complicated and its performance depends on a number of factors, such as vibration level, granular material properties, packing ratio, etc. In this study, free vibration experiments are conducted on a cantilevered beam incorporated with granular damping. A signal analysis approach based on the Hilbert transform (HT) is then employed to identify the nonlinear damping characteristics from the acquired responses, such as the dependency of the natural frequency and damping ratio on the vibration level. This HT based analysis can produce an effective temporal-frequency amplitude∕energy analysis, which provides us with physical insights of the nonlinear transient response. A direct comparison between the granular damping and the impact damping (with single impactor to dissipate vibratory energy) is performed to highlight the difference between these two and the advantages of granular damping. Finally, the validity of the proposed approach is also examined by the successful prediction of vibration response using the extracted granular damping characteristics.

scholarly journals Research on Damping Characteristics of Interconnected Hydropneumatic Suspension considering the Effects of Hose and Check Valve

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Hongmin Zhang ◽  
Xin Fang
Keyword(s):  
Numerical Simulation ◽  
Energy Method ◽  
Damping Ratio ◽  
Check Valve ◽  
Nonlinear Stiffness ◽  
Calculation Formula ◽  
Damping Force ◽  
Damping Characteristics ◽  
Simulation Results ◽  
Stiffness And Damping

The interconnected hydropneumatic suspension (ICHPS) has not only the nonlinear stiffness and damping of the independent hydropneumatic suspension (IDHPS) but also antiroll and antipitch functions. The existing analysis of hydropneumatic suspension damping mainly focuses on the orifice and check valve in the suspension cylinder. In this study, the calculation formula of the damping force of ICHPS is established, and the numerical simulation results show that the damping characteristics of the hydraulic hose cannot be ignored. The influence of check valve and hose on the damping characteristics is analyzed. Through the equivalent energy method, the equivalent compression damping ratio and the equivalent recovery damping ratio of the ICHPS are established. It is pointed out that when designing the damping characteristics of the ICHPS, it is necessary to select the orifices, check valves, and hose damping reasonably to make the damping characteristics get the best match.

scholarly journals Numerical simulation of cavitation characteristics in high speed water entry of head-jetting underwater vehicle

2021 ◽  
Vol 39 (4) ◽  
pp. 810-817
Author(s):  
Hairui Zhao ◽  
Yao Shi ◽  
Guang Pan
Keyword(s):  
Numerical Simulation ◽  
High Speed ◽  
Impact Load ◽  
Underwater Vehicle ◽  
Water Entry ◽  
Engineering Practice ◽  
Entry Angle ◽  
Air Jet ◽  
Entry Velocity ◽  
The Impact

Autonomous underwater vehicle will be subjected to a huge impact load during high speed water entry, which will damage the structure and the internal instruments of the vehicle. Therefore, it is of great significance to study the buffer mechanism of the vehicle during the process of water-entry. In this paper, a kind of head-jetting device with disk cavitation is used. The complex cavitation forms, under the three-phase coupling of gas, liquid and solid, in the water entry process of the vehicle on which the device is installed. In this paper, the numerical simulation of high-speed water entry of the vehicle equipped with head jet device is carried out. Through the analysis of water entry cavitation under typical working conditions, the following conclusions are obtained. After the installation of head jet device, the water entry cavity of the vehicle changes gradually from cone to spindle shape. The air jet, compared with that without jet, can promote the formation of water inlet supercavitation, decrease the interaction area between the vehicle and water, and reduce the impact load during water entry. At the same water entry depth, the diameter of cavitation increases with the amount of air jet. The water entry velocity has a great influence on the difference of cavitation shape. The water entry depth closure phenomenon, when the water entry velocity is less than 100 m/s, can be observed in the depth of 3.5 times of the projectile length. The water entry angle has a significant effect on the cavitation shape. The cavity shows obvious asymmetry when the vehicle slants into the water, and the diameter and length of the bubbles decrease with the increase of the water entry angle. The research content of this paper provides technical support for the engineering practice of high-speed water entry and load reduction, and the conclusions are of great significance in related fields.

Analysis of Granular Damping Using Hilbert Transform Based Technique

2007 ◽  
Author(s):  
X. Fang ◽  
H. Luo ◽  
J. Tang
Keyword(s):  
Hilbert Transform ◽  
Damping Ratio ◽  
Temporal Frequency ◽  
Nonlinear Damping ◽  
Vibration Level ◽  
Damping Characteristics ◽  
The Difference ◽  
The Hilbert Transform ◽  
Granular Damping ◽  
The Impact

Granular damping results from a combination of energy dissipation mechanisms including the impact and the friction between the vibrating structure and granules and among the granules. Although simple in concept, granular damping is very complicated and its performance depends on a number of factors, such as vibration level, granular material properties, and packing ratio, etc. In this study, free vibration tests are conducted on a cantilevered beam incorporated with granular damping. A signal analysis approach based on the Hilbert transform (HT) is then employed to identify the nonlinear damping characteristics from the acquired responses, such as the dependency of the natural frequency and damping ratio on vibration level. This HT based analysis can produce an accurate temporal-frequency amplitude/energy analysis which provides us with physical insights of the nonlinear transient response. A direct comparison between the granular damping and the impact damping (with single impactor to dissipate vibratory energy) is performed to highlight the difference between these two as well as the advantages of granular damping. Finally, validity of the proposed approach is also examined by the successful prediction of vibration response using the extracted granular damping characteristics.

The Effect of Longitudinal Center of Gravity Position on the Sway Stability of a Small Cargo Trailer

2008 ◽  
Author(s):  
Michael G. Gilbert ◽  
Daniel A. Godrick ◽  
Richard H. Klein
Keyword(s):  
Dynamic Response ◽  
Damping Ratio ◽  
Leaf Spring ◽  
Loading Conditions ◽  
Novice Drivers ◽  
Training Requirements ◽  
Mandatory Training ◽  
Damping Characteristics ◽  
The Stability ◽  
The Impact

Small and mid-sized cargo trailers are often used to transport goods by people with limited experience in loading trailers and driving vehicles with trailers attached. This paper examines the effect of front to rear load position on the stability of a trailer by measuring its dynamic response to a variety of steer inputs at several different highway speeds. Additionally, tests with varying steers and speeds were performed with a simulated suspension malfunction to study the trailer’s dynamic response to this condition. Trailer sway has been a well-documented trailer characteristic for decades. However there are no special driver’s licensing or mandatory training requirements for even large trailers and campers. The trailer chosen for this test was a lightweight double axle cargo trailer commonly rented by people with limited to no towing experience. This consumer is likely to be unfamiliar with the best practices of trailer loading. This consumer is also likely a non-professional driver with little to no towing experience in the event of encountering unexpected trailer sway. Therefore it was the goal of the authors to determine how the stability of this type of trailer varies with different front to rear loading conditions and speeds to see if it is safe to operate on the highways by novice drivers. Trailer sway stability was determined by measuring the trailer sway (articulation) response during repeated, pulse steer tests. The trailer sway damping characteristics were measured, as a “damping ratio”, for six different hitch loads that corresponded to six different longitudinal loading conditions. These conditions, expressed as % load forward of the trailer centerline / % load aft of the trailer centerline were: 65/35, 60/40, 55/45, 50/50, 45/55, and 40/60. These loading conditions were tested per SAE J2664 [1] protocol. The resulting trailer sway characteristics for each loading condition then were compared to published trailer sway stability criteria [2, 3] to determine the suitability of this particular tow vehicle-trailer combination for use by the public in a rental market. The impact of a suspension malfunction on the trailer stability was also studied. This consisted of a detachment of one rear leaf spring hanger.

NUMERICAL SIMULATION STUDY ON BIONIC MUCUS DRAG REDUCTION OF UNDERWATER VEHICLE

2020 ◽  
Vol 47 (4) ◽  
pp. 371-385
Author(s):  
Kaisheng Zhang ◽  
Chaofan Ma ◽  
Baocheng Zhang ◽  
Bo Zhao ◽  
Qiang Wang
Keyword(s):  
Numerical Simulation ◽  
Drag Reduction ◽  
Simulation Study ◽  
Underwater Vehicle
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