• 제목/요약/키워드: hydrodynamic pressure

검색결과 482건 처리시간 0.026초

Buckling failure of cylindrical ring structures subjected to coupled hydrostatic and hydrodynamic pressures

  • Ping, Liu;Feng, Yang Xin;Ngamkhanong, Chayut
    • Structural Monitoring and Maintenance
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    • 제8권4호
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    • pp.345-360
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    • 2021
  • This paper presents an analytical approach to calculate the buckling load of the cylindrical ring structures subjected to both hydrostatic and hydrodynamic pressures. Based on the conservative law of energy and Timoshenko beam theory, a theoretical formula, which can be used to evaluate the critical pressure of buckling, is first derived for the simplified cylindrical ring structures. It is assumed that the hydrodynamic pressure can be treated as an equivalent hydrostatic pressure as a cosine function along the perimeter while the thickness ratio is limited to 0.2. Note that this paper limits the deformed shape of the cylindrical ring structures to an elliptical shape. The proposed analytical solutions are then compared with the numerical simulations. The critical pressure is evaluated in this study considering two possible failure modes: ultimate failure and buckling failure. The results show that the proposed analytical solutions can correctly predict the critical pressure for both failure modes. However, it is not recommended to be used when the hydrostatic pressure is low or medium (less than 80% of the critical pressure) as the analytical solutions underestimate the critical pressure especially when the ultimate failure mode occurs. This implies that the proposed solutions can still be used properly when the subsea vehicles are located in the deep parts of the ocean where the hydrostatic pressure is high. The finding will further help improve the geometric design of subsea vehicles against both hydrostatic and hydrodynamic pressures to enhance its strength and stability when it moves underwater. It will also help to control the speed of the subsea vehicles especially they move close to the sea bottom to prevent a catastrophic failure.

삼엽식 인공판막의 수력학적 성능평가에 관한 연구 (A Study on the Evaluation of Hydrodynamic Performance of Trileaflet Prosthetic Heart Valves)

  • 김혁필;이계한
    • 대한의용생체공학회:의공학회지
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    • 제18권2호
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    • pp.147-156
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    • 1997
  • Various prosthetic heart valves have been developed and used clinically, but they have problems, such as thrombogenecity, hemoltsis, high cost and low durability. New types of trileaflet polymer heart valves have been developed in order to use them as inlet and outlet valves in a ventricular assist device. The aim of this study is to determine the hydrodynamic effectiveness of the newly designed trileaflet polymer valves and their feasibility for temporary use in the blood pumps. Trileaflet polymer valves are made of polyurethane, because of its good blood compatibility, high tonsil strength and good resistance to fatigue. An in vitro experimental investigation was perf'ormed in order to ev91ua1e hydrodynamic performance of the trileaflet polymer valves having different design and fabrication tech- niques. The St. Jude Medical valve (SJMV) and floating-type monoleaflet polymer valve (MLPV) were also tested The pressure drop across the valve, leakage volume, and the flow patterns mere investigated for valves. The result of comparative tests showed that the trileaflet polymer valves had a better hydrodynamic performance than the others. TPV which has two stable membrane shape showed the lowest back flow. The pressure hops of TPVs were lower than that of MLPV, but slightly higher than SJMV. The hydrodynamic performance of valves under the pulastile flow showed the similar results as steady flow. The velocity profiles and turbulent intensities were measured at the distal sites of valves using a hot-film anemometer. Central flow was maintained in trileaflet polymer valves, and the maximum turbulent intensities were lower in TPVs comparing to MLPV.

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EXPERIMENTAL INVESTIGATION OF PRESSURE FLUCTUATIONS ON THE BED OF FLIP BUCKET SPILLWAYS

  • KAVIANPOUR M.R.;POURHASAN M.A.
    • 한국수자원학회:학술대회논문집
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    • 한국수자원학회 2005년도 학술발표회(1)
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    • pp.590-591
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    • 2005
  • Hydrodynamic pressure fluctuations and their roles on the design of hydraulic structures has been the subject of many investigations. The studies showed that turbulent pressure fluctuations may cause serious damages to hydraulic structures. In case of high velocity flows, separation of flow from the boundary also causes the local pressure to drop and as a result, the resultant pressure fluctuations may trigger cavitation. Sever hydrodynamic pressures are also associated with the vibration of structures. Therefore, in this work, experiments were performed to determine the intensity of pressure fluctuations and their distribution along the bed of a ski-jump flip bucket. Experiments were completed on a physical model at the Institution of Water Research of Iran. The results consist of the statistical characteristics of pressure fluctuations, its maximum, minimum, and r.m.s values along the bed of the bucket. The spectral analysis of pressure fluctuations which is useful for the instability analysis of such structures is also provided. It is hoped that the present results will help the designer of such structures.

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수학적 해석 방법에 의한 액체저장탱크의 액동압 거동 해석 (Hydrodynamic Behavior Analysis of Vertical-Cylindrical Liquid-Storge Tanks by Mathematically Analytic Method)

  • 박종률;오택열
    • 대한기계학회논문집A
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    • 제26권3호
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    • pp.487-496
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    • 2002
  • Hydrodynamic behavior and response of vertical-cylindrical liquid-storage tank is considered. The equation of the liquid motion is shown by Laplace's differential equation with the fluid velocity potential. The solution of the Laplace's differential equation of the liquid motion is expressed with the modified Bessel functions. Only rigid tank is studied. The equivalent masses and heights for the tank contents are presented for engineering design model.

Q1D modeling of hydrodynamic instabilities in solid rocket motors

  • M., Grossi;D., Bianchi;B., Favini
    • Advances in aircraft and spacecraft science
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    • 제9권5호
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    • pp.479-491
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    • 2022
  • This work concerns the investigation of a Q1D methodology employed to study pressure oscillations in solid rocket motors driven by hydrodynamic instabilities. A laboratory-scale solid motor designed to develop vortex-shedding phenomena is analyzed for the whole firing time. The comparison between numerical results and experimental data shows good agreement regarding pressure oscillations signature, especially in the flute-mode behavior, the typical oscillations frequency trend present in any motor liable to hydrodynamic instabilities. Such result ensures the model capability to cope with this particular kind of pressure oscillations source, allowing the investigation of the phenomenon with a lighter and cost savings methodology than CFD simulations.

Hydrodynamic performance of a pump-turbine model in the "S" characteristic region by CFD analysis

  • Singh, Patrick Mark;Chen, Chengcheng;Choi, Young-Do
    • Journal of Advanced Marine Engineering and Technology
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    • 제39권10호
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    • pp.1017-1022
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    • 2015
  • Specific hydrodynamic characteristic of pump-turbine during the start and load rejection process of generating mode causes anomalous increase of water pressure, along with large machine vibration, called "S" characteristic. The aim of this study is to understand and explain the hydrodynamic performance of pump-turbine at "S" characteristic region by using a model of pump-turbine system. The operation in the condition of runway and low discharge in a typical "S" characteristic curve may become unstable and complex flow appears at the passage of guide vane and impeller. Therefore, velocity and pressure distribution are investigated to give an all-sided explanation of the formation and phenomenon of this characteristic, with the assistance of velocity triangle analysis at the impeller inlet. From this study, the internal flow and pressure fluctuation at the normal, runway and low discharge points are explored, giving a deep description of hydrodynamic characteristic when the pump-turbine system operates with "S" characteristic.

SMART 유동혼합헤더집합체의 동수력 질량 특성 고찰 (Investigation of Hydrodynamic Mass Characteristic for Flow Mixing Header Assembly in SMART)

  • 이규만;안광현;이강헌;이재선
    • 한국압력기기공학회 논문집
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    • 제16권1호
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    • pp.30-36
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    • 2020
  • In SMART, the flow mixing header assembly (FMHA) is used to mix the coolant flowing into the reactor core to maintain a uniform temperature. The FMHA is designed to have enough stiffness so the resonance with reactor internal structures does not occurs during the pipe break and the seismic accidents. Since the gap between the FMHA and the core support barrel assembly is very narrow compared with the diameter of FMHA, the hydrodynamic mass effect acting on the FMHA is not negligible. Therefore the hydrodynamic mass characteristics on the FMHA are investigated to consider the fluid and structure interaction effects. The result of modal analysis for the dry and underwater conditions, the natural frequency of primary vibration mode for the horizontal direction is reduced from 136.67 Hz to 43.76 Hz. Also the result of frequency response spectrum seismic analysis for the dry and underwater conditions, the maximum equivalent stress are increased from 13.89 MPa to 40.23 MPa. Therefore, reactor internal structures located in underwater condition shall consider carefully the hydrodynamic mass effects even though they have sufficient stiffness required for performing its functions under the dry condition.

Analysis and Test of Hydrodynamic Ram in Welded Metallic Water Tanks

  • Kim, Jong Heon;Kim, Chun-Gon;Jun, Seungmoon
    • International Journal of Aeronautical and Space Sciences
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    • 제16권1호
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    • pp.41-49
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    • 2015
  • Analysis and test of hydrodynamic ram in welded metallic tanks containing water were performed to investigate the phenomena and to understand the effects on the resulting structural behavior. Arbitrary Lagrange-Euler coupling method was used for the analysis of the fluid-structure interaction occurring in the hydrodynamic ram, where the projectile, tank, and water are exchanging load, momentum, and energy during the traveling of the projectile through the water of the tank. For a better representation of the physical phenomena, modeling of the welded edges is added to the analysis to simulate the earlier weld line fracture and its influence on the resulting hydrodynamic ram behavior. Corresponding hydrodynamic tests were performed in a modified gas gun facility, and the following panel-based examinations of various parameters, such as displacement, velocity, stress, and energy, as well as hydrodynamic ram pressure show that the analysis and test are well correlated, and thus the results of the study reasonably explain the characteristics of the hydrodynamic ram. The methodology and procedures of the present study are applicable to the hydrodynamic ram assessment of airframe survivability design concepts.

Chine형(型) 선체(船體)의 상하진동시(上下振動時) 선체표면(船體表面)에 작용(作用)하는 유체압력(流體壓力)에 관(關)한 고찰(考察) (On the Two-Dimensional Hydrodynamic Pressure on the Hull Surface of the Chine-Type Ship in Vertical Vibration)

  • 김극천
    • 대한조선학회지
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    • 제6권2호
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    • pp.11-16
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    • 1969
  • Chine형(型) 선체(船體)의 상하진동시(上下振動時) 수선하(水線下) 선체표면(船體表面)에 작용(作用)하는 2차원적(次元的) 유체압력(流體壓力)의 분포특성(分布特性)을 고찰(考察)할 목적(目的)으로 앞서 발표(發表)한 논문(論文) [1]에서 채용(採用)했던 Chine형(型) 선체단면형상(船體斷面形狀)을 주는 2경수군(徑數群) 등각사상함수(等角寫像函數)를 이용(利用)하여 변동압력(變動壓力)의 분포(分布)를 계산(計算)하고 이를 Hypotrocoid성질(性質)을 갖는 Lewis form, 원단면(圓斷面), 타원단면(楕圓斷面), 삼각형단면(三角形斷面) 및 사각형단면(四角形斷面) 등(等) 여러 가지 다른 단면형상(斷面形狀)을 가지는 주상체(柱狀體)들의 경우(境遇)와 비교검토(比較檢討)하였다.

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Hydrodynamic approach to cosmic ray acceleration

  • KO CHUNG-MING
    • 천문학회지
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    • 제34권4호
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    • pp.289-291
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    • 2001
  • To study the structure and dynamics of a cosmic-ray-plasma system, hydrodynamic approach is a fairly good approximation. In this approach, there are three basic energy transfer mechanisms: work done by the plasma flow against pressure gradients, cosmic ray streaming instability and stochastic acceleration. The interplay between these mechanisms gives a range of structures. We present some results of different version of the hydrodynamic approach, e.g., flow structure, injection, instability, acceleration with and without shocks.

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