scholarly journals Effect of Waves on the Behavior of Emergent Buoyantly Rising Submarines Using CFD

2020 ◽  
Vol 10 (23) ◽  
pp. 8403
Author(s):  
Qinglong Chen ◽  
Hongwei Li ◽  
Shudi Zhang ◽  
Jian Wang ◽  
Yongjie Pang ◽  
...  
Keyword(s):  
Water Surface ◽  
Roll Angle ◽  
Head Wave ◽  
Longitudinal Motion ◽  
Wave Direction ◽  
Initial Angle ◽  
Slight Effect ◽  
Bow Wave ◽  
Static Water ◽  
The Difference

Emergent buoyantly rising submarines encounter excess roll problems, partially owing to waves that significantly affect their behavior. This study predicts the behavior of a submarine, including when it rises in static water, beam sea, head wave, following wave, 30∘ bow wave, 60∘ bow wave, 30∘ quartering wave, and 60∘ quartering wave, using the computational fluid dynamics method. The beam sea has a slight effect on pitch prior to the submarine rising to the water surface, but the maximum roll angle in the beam sea is 4.43 times that in static water. After a submarine submerges in water, the pitching oscillation does not decay quickly owing to the yaw angle. The head wave and the following wave have a continuous significant effect on the pitch; the submarine sail remains under the water surface after it submerges from the highest position. The head wave and the following wave have a slight effect on the roll and yaw before the submarine rises to the water surface; however, the roll angle suddenly increases after the submarine submerges from the highest position. As the initial angle between the submarine centerline and wave direction increases, the effect of waves on the longitudinal motion decreases. The amplitude of the pitching oscillation decreases with an increase in the initial angle between the submarine centerline and wave direction, and the waterline when the submarine oscillates on the water surface decreases. The difference in the maximum roll angle between when a submarine rises in an oblique wave and when it rises in beam sea is below 6.3∘. Submarines should try to avoid rising in a head wave and the following wave.

Numerical and Experimental Approaches to Investigate the Stability of a Motorcycle Vehicle

2006 ◽  
Author(s):  
Federico Cheli ◽  
Marco Bocciolone ◽  
Marco Pezzola ◽  
Elisabetta Leo
Keyword(s):  
Degrees Of Freedom ◽  
Structural Parameters ◽  
Experimental Tests ◽  
Roll Angle ◽  
Longitudinal Motion ◽  
Reference Trajectory ◽  
Steering Angle ◽  
Steady State Condition ◽  
The Stability ◽  
Linearized Model

The study of motorcycle’s stability is an important task for the passenger’s safety. The range of frequencies involved for the handling stability is lower than 10 Hz. A numerical model was developed to access the stability of a motorcycle vehicle in this frequency range. The stability is analysed using a linearized model around the straight steady state condition. In this condition, the vehicle’s vertical and longitudinal motion are decoupled, hence the model has only four degrees of freedom (steering angle, yaw angle, roll angle and lateral translation), while longitudinal motion is imposed. The stability was studied increasing the longitudinal speed. The input of the model can be either a driver input manoeuvre (roll angle) or a transversal component of road input able to excite the vibration modes. The driver is introduced in the model as a steering torque that allows the vehicle to follow a reference trajectory. To validate the model, experimental tests were done. To excite the vehicle modes, the driver input was not taken into account considering both the danger for the driver and the repeatability of the manoeuvre. Two different vehicle configurations were tested: vehicle 1 is a motorcycle [7] and vehicle 2 is a scooter. Through the use of the validated model, a sensitivity analysis was done changing structural (for example normal trail, steering angle, mass) and non structural parameters (for example longitudinal speed).

scholarly journals Result of modeling temperature anomalies on the water surface of the research basin of the institute of hydromechanics NAS of Ukraine

2018 ◽  
pp. 40-45
Author(s):  
Oleksandr Fedorovsky ◽  
Vitalii Filimonov ◽  
Iryna Piestova ◽  
Stanislav Dugin ◽  
Vladyslav Yakymchuk ◽  
...  
Keyword(s):  
Water Surface ◽  
Water Layer ◽  
Sea Surface ◽  
National Academy Of Sciences ◽  
Near Surface ◽  
Aerial Photos ◽  
Temperature Anomalies ◽  
Structural And Textural Parameters ◽  
The Difference ◽  
Hydrocarbon Deposits

The results of the research and physical modeling of temperature anomalies of natural or man-made origin on the water surface are presented.  The information for the research was obtained from the experimental basin of the Institute of Hydromechanics of the National Academy of Sciences of Ukraine from the self-propelled model as the generator of hydrodynamic processes. The information obtained after image processing allowed to significantly expand the existing ideas about the mechanism of formation of anomalies on the open surface with the hydrodynamic disturbances from hydrocarbon deposits and moving submerged object. The interaction of the emerging hydrodynamic disturbances with the near-surface water layer and the occurrence of unmasking temperature anomalies on the open sea surface have a lot in common between the hydrocarbon deposits and the moving submerged object. The application of the difference of the above structural and textural parameters by calculating the value of "entropy" has been proposed as the informative feature for decoding the images of the water surface with the presence of hydrocarbon deposits or moving immersed objects. The decoding of temperature anomalies consists of two stages: learning and proper decoding. The first stage is the supervised learning, during which the system is being researched using the existing set of images, in which only the background and no hydrocarbon deposits or moving submerged object. Training is carried out in order to determine the signs of belonging to the background or hydrocarbon deposits, moving submerged object. It was determined that the background has minimal entropy values, and with the appearance of an anomaly, the entropy grows to the maximum value, after which, as the temperature trace dissipates, it begins to fall to background values. This confirms the informativity of the entropy feature for decoding the optical anomalies of man-made and natural origin on the sea surface from aerial photos.

scholarly journals CHARACTERISTICS OF UHF WAVES DISTRIBUTION IN LAND AND WATER SURFACE TROPOSPHERIC WAVEGUIDE

2019 ◽  
pp. 115-121
Author(s):  
Oxana Vladimirovna Kalambatskaya ◽  
Oleg Nickolaevich Pishchin
Keyword(s):  
Communication Systems ◽  
Water Surface ◽  
Sea Water ◽  
Systems Design ◽  
Cellular Communication ◽  
Effect Of Temperature ◽  
Radio Waves ◽  
Wave Direction ◽  
Surface Atmospheric Layer ◽  
Cellular Communication Systems

The article considers examples of ultra-long propagation of UHF radio waves in mobile cellular communication systems. The phenomena are mainly observed in the Astrakhan region in the spring-summer period (May-June) and are presumably associated with sharp seasonal changes of air temperature followed by rains. The effect of temperature inversion results in changing the refraction index in the surface layer and, as a result, in changing the wave direction as the effect of superrefraction in the surface atmospheric layer. The properties of radio waves in their propagation in the land and sea-water surface waveguide are investigated. The values of the heights of land and sea-water surface tropospheric waveguides for cellular communication systems of different ranges are obtained. The features of existing of tropospheric land and sea-water surface tropospheric waveguides are described. The need to use their properties in the mobile communication systems design is stated.

Extraction of Tsunami-Flooded Areas and Damaged Buildings in the 2011 Tohoku-Oki Earthquake from TerraSAR-X Intensity Images

2013 ◽  
Vol 29 (1_suppl) ◽  
pp. 183-200 ◽  
Author(s):  
Wen Liu ◽  
Fumio Yamazaki ◽  
Hideomi Gokon ◽  
Shun-ichi Koshimura
Keyword(s):  
High Resolution ◽  
Emergency Management ◽  
Emergency Response ◽  
Water Surface ◽  
Tohoku Earthquake ◽  
Visual Interpretation ◽  
Automated Method ◽  
Intensity Images ◽  
The Difference ◽  
Flooded Areas

The Tohoku earthquake of 11 March 2011 caused very large tsunamis and widespread devastation. Various high-resolution satellites captured details of affected areas and were utilized in emergency response. In this study, high-resolution pre- and post-event TerraSAR-X intensity images were used to identify tsunami-flooded areas and damaged buildings. Since water surface generally shows very little backscatter, flooded areas could be extracted by the difference of backscattering coefficients between the pre- and post-event images. Impacted buildings were detected by calculating the difference and correlation coefficient within the outline of each building. The damage estimates were compared with visual interpretation results, which suggest that the overall accuracy of the proposed method for flooded areas was 80%, and for damaged buildings was 94%. Since the proposed half-automated method takes less processing time and is applicable to various cases, it is expected to provide quick and useful information in emergency management.

A Simplified Dynamic Model for the Analysis of the Slider Off-Track Motion Due to Head-Disk Interactions

2009 ◽  
Vol 131 (2) ◽  
Author(s):  
Yanhui Yuan ◽  
Shao Wang
Keyword(s):  
Contact Force ◽  
Rotational Speed ◽  
Disk Drive ◽  
Roll Angle ◽  
Transverse Motion ◽  
Transverse Displacement ◽  
Skew Angle ◽  
The Coefficient Of Friction ◽  
The Difference ◽  
Displacement Based

A five-degree-of-freedom model was developed for the analysis of the off-track motion of the magnetic head slider in a hard disk drive. The air bearing was integrated into the dynamic system by combining its stiffness and damping matrices with those of the suspension. Simulation was conducted for the slider in intermittent contact with circumferentially located bumps on a rotating magnetic disk. For a single bump, the excitation to the transverse displacement of the slider is close to that of an impulse. However, for multiple bumps in a sequence, the excitation gives an effect similar to that of a step force function. The maximum transverse displacement increases almost linearly with both the coefficient of friction and the skew angle. The average contact force is determined by the maximum contact force, the contact time ratio, and the shape factor of the contact force, which change with the bump spacing and the rotational speed of the disk. The steady-state transverse displacement is related to the average contact force. As the bump spacing decreases, the average contact force increases, resulting in a greater transverse displacement. Based on the system dynamic characteristics alone, changing the rotational speed of the disk has only a small impact on the average contact force and, thus, on the transverse displacement. At zero skew angle with the bump path close to a rear pad edge, significant transverse motion occurs because of the excited roll mode and the coupling between the roll angle and the transverse displacement. The off-track motion of the slider is dominated by the rotational mode of the actuator arm and the sway mode of the suspension, as verified by comparing the results of the transverse displacement from the 5DOF model to that from a 2DOF model of the transverse motions of the actuator arm and suspension. The effects of the roll angle on the transverse displacement through coupling were found to be responsible for the difference in the transverse displacements obtained from the two models.

scholarly journals Acceleration and the “clock paradox”.

1961 ◽  
Vol 2 (1) ◽  
pp. 120-121 ◽  
Author(s):  
C. A. Hurst
Keyword(s):  
Slight Effect ◽  
Orthodox Interpretation ◽  
Clock Paradox ◽  
The Difference ◽  
The Universe

In the controversy which has been continuing over the “clock paradox”, it has been claimed by supporters ([1]) of the orthodox interpretation that the difference in behaviour of clocks carried by observers in motion relative to each other can be traced to differencesin the motion relative to the universe. Whilst A remains unaccelerated relative to the universe, B for a portion of his journey does not. Professor Dingle, in reply ([2]), remarked that he would “not dispute a possible slight effect” but could not understand why, if the acceleration of B were so important, it did not appear explicitly in the answer.

On Wind-Wave Misalignment, Directional Spreading and Wave Loads

2013 ◽  
Author(s):  
Gerbrant Ph. Van Vledder
Keyword(s):  
Numerical Modeling ◽  
Wind Wave ◽  
Offshore Structures ◽  
Integration Time ◽  
Wave Loads ◽  
Wave Direction ◽  
Time Step ◽  
The Difference ◽  
Wind Sea ◽  
Spectral Partitioning

Causes of wind-wave misalignment, the difference between wind and mean wave direction, are investigated for stationary and non-stationary situations using numerical modeling. This includes the effects of upwind fetch restrictions, refraction, choice of source terms and integration time step on wind-wave misalignment are illustrated. A statistical analysis is performed to quantify wind-wave misalignment as a function of wind speed and significant wave height. In addition, the effect of spectral partitioning in separate wind sea and swell systems on the statistics of wind-wave misalignment is illustrated. Apart from the differences in mean direction, attention is given to the associated directional spreading. Implications for the design of offshore structures and the movements of moored ships are discussed.

Preparation of Thin Polycarbonate Film and Its Application to PIXE Analysis of Anionic Elements in Water Samples

1997 ◽  
Vol 07 (01n02) ◽  
pp. 101-108 ◽  
Author(s):  
H. Yamazaki ◽  
K. Tsutsumi ◽  
K. Ishii ◽  
S. Matsuyama ◽  
K. Murozono ◽  
...  
Keyword(s):  
Water Surface ◽  
Film Formation ◽  
Internal Standard ◽  
Good Combination ◽  
Pixe Analysis ◽  
Casting Solution ◽  
Anionic Species ◽  
Target Frame ◽  
Polycarbonate Film ◽  
The Difference

A polycarbonate film of thin and uniform thickness was prepared. A casting solution for film-formation was made up by diluting a solution of poly (bisphenol A carbonate) in chloroform by a factor of two to three with benzene. A uniform film was created by dropping 0.2-0.3 cm3 of the casting solution slowly on a water surface within an aperture (20 mm diameter) of Mylar target frame floating on 50 wt% sucrose aqueous solution. Films of 0.14-0.27 mg/cm2 thickness thus prepared offer a good combination of mechanical strength and low continuum backgrounds. To test PIXE analysis of anionic species in water, targets containing SO 42-, Cr 2 O 72-, AsO 43-, and Ga 3+-internal standard were prepared by depositing 100 μl of the test solutions onto the polycarbonate film, and irradiated in vacuum by 3 MeV proton beams. The difference between the nominal and the analyzed concentrations seldom exceeded ± 15 % in the range from 10 to 2000 ppb.

Mechanical Control of Oil Spills Utilizing a Streamlined Boom

1973 ◽  
Vol 1973 (1) ◽  
pp. 383-389
Author(s):  
David C. Wooten
Keyword(s):  
Drag Coefficient ◽  
Oil Spill ◽  
Water Surface ◽  
Oil Spills ◽  
Collection Efficiency ◽  
Leading Edge ◽  
Oil Retention ◽  
Bow Wave ◽  
Over The Top ◽  
Conventional Oil

ABSTRACT Conventional oil retention booms fail to contain oil in currents above one to two knots. A steamlined boom to operate in currents or while being towed in excess of two knots was designed and tested under varying current and combined wave-current conditions. The boom consists of airfoil-shaped sections which resemble hydrofoils operating at the water surface. The boom is designed so that the stagnation streamline at the leading edge of the foil is located beneath the oil spill under a range of dynamic current and wave conditions. Motion of the boom through the water (or the flow past the boom due to a net current) causes a bow wave which sweeps oil and water over the top of the leading edge of the boom and into a sump. Tests indicated that the streamlined boom profile has a drag coefficient of less than one-third that of conventional boom shapes. Collection efficiency measurements with oil indicate that collection efficiencies greater than 75 percent can be achieved at three knots.

Establishment of the Bow-Wave in the Supersonic Flow of Carbon Dioxide Past a Sphere

1968 ◽  
Vol 19 (1) ◽  
pp. 51-58 ◽  
Author(s):  
H. K. Zienkiewicz ◽  
I. D. Malloch
Keyword(s):  
Carbon Dioxide ◽  
Experimental Study ◽  
Supersonic Flow ◽  
Shock Tube ◽  
Vibrational Relaxation ◽  
Incident Shock ◽  
Slight Effect ◽  
Schlieren Technique ◽  
Bow Wave ◽  
Made In

SummaryAn experimental study of bow-wave trajectories for a sphere in CO2 has been made in a shock tube, using a drum-camera-schlieren technique, for incident shock Mach numbers of 2·4, 2·8 and 4·0. Results show that vibrational relaxation has only a slight effect on the bow-wave formation time but significantly affects the stand-off distance in steady flow.

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