• Title/Summary/Keyword: Unsteady Flow

Search Result 785, Processing Time 0.228 seconds

A Study of Artificial Reef Subsidence in Unsteady Flow-Wave Field (비정상 흐름-파랑 공존장의 인공어초 침하특성에 관한 연구)

  • Yun, Sang Jun;Kim, Heon Tae
    • Journal of Ocean Engineering and Technology
    • /
    • v.15 no.3
    • /
    • pp.28-34
    • /
    • 2001
  • The experimental studies for the artificial reef (AFR) subsidence characteristics in the unsteady flow field and in the unsteady flow-wave field were carried out. The difference of scou $r_sidence characteristics between in the steady flow field and in the unsteady flow field wad discussed and also the long-term subsidence characteristics in the unsteady flow field were investigated. AFR subsidence characteristics was discussed with Keulegan - Carpenter number(KC), Reynolds number (Re),. Shields number (Sn) and dimensionless time (t/Tt). And the difference of subsidence characteristics between in the unsteady flow and in the unsteady flow-wave field was discussed.ed.

  • PDF

Flood Analysis by Unsteady Flow on Tidal River Estuary (부정류에 의한 감조하천의 홍수분석)

  • 김현영
    • Magazine of the Korean Society of Agricultural Engineers
    • /
    • v.32 no.4
    • /
    • pp.81-88
    • /
    • 1990
  • The flow in a river reach where is influenced by tidal motion is characterized by unsteady flow. The flood analysis in the river reach needs depending upon the theory based on the complete unsteady flow equations. In this study the unsteady flow model which is called CRIUM (Channel Routing by Implicit Unsteady Flow Model) was developed and was applied to the Mankyong and Dongjin river in order to analyze the flood characteristics. The results, which were calibrated and verified by the flood records to be measured in the two rivers, show that unsteady flow mode] can be used for the derivation of the flood hydrograph. The peak flood discharges were estimated as 4,960 and $2,870m^3$/sec in 100 year frequency at the estuary of the Mankyong and Dongjin river, respectively. In addition, it was analyzed that the river reaches were not influenced by tidal motion when the discharge magnitude was larger than approximately $3,000m^3$/sec.

  • PDF

Unsteady Flow Rate Measurement by Using Hydraulic Pipeline Dynamics (유압관로의 동특성을 이용한 비정상 유량계측)

  • 김도태
    • Proceedings of the Korean Society of Machine Tool Engineers Conference
    • /
    • /
    • pp.411-416
    • /
    • 1999
  • The measurement of unsteady flow rate is of vital importance to clarify and improve the dynamic characteristics in pipeline, hydraulic components and system. There is also demand for a real time flow sensor of ability to measure unsteady flow rate with high accuracy and fast response to realize feedback control of flow rate in fluid power systems. In this paper, we propose an approach for estimating unsteady flow rate through a pipeline and components under high pressure condition. In the method, unsteady flow rate is estimated by using hydraulic pipeline dynamics and the measured pressure values at two distant points along the pipeline. The distributed parameter model of hydraulic pipeline is applied with consideration of frequency dependent viscosity friction and unsteady velocity distribution at a cross section of a pipeline. By using the self-checking functions of the method, the validity is investigated by comparison with the measured and estimated pressure waveforms at the halfway section on the pipeline. The results show good agreement between the estimated flow rate waveforms and theroetical those under unsteady laminar flow conditions. the method proposed here is useful in estimating unsteady flow rate through an arbitray cross section in hydraulic pipeline and components without installing an instantaneous flowmeter.

  • PDF

Hydraulic Behavior and Characteristic Analysis by Steady & Unsteady Flow Analysis of Natural Stream (하도 합류부의 정류.부정류해석에 따른 수리학적 변화 특성 분석)

  • Ahn, Seung-Seop;Yim, Dong-Hee;Park, Ro-Sam;Kwak, Tae-Hwa
    • Journal of Environmental Science International
    • /
    • v.17 no.9
    • /
    • pp.957-968
    • /
    • 2008
  • The purpose of this study is to analyze the characteristics of hydraulic behavior of the natural channel flow according to the temporal classification mode, and thus propose the hydraulic analysis method for future channel design. For analysis, the temporal flow characteristics of the channel section was divided into the steady flow and the unsteady flow. For hydraulic analysis, the HEC-RAS model, which is a one-dimensional numerical analysis model, and the SMS-RAM2 model, which is a two-dimensional model, were used and the factors used for analysis of hydraulic characteristics were flood elevation and flow rate. The flow state was analyzed on the basis of the one-dimensional steady flow and unsteady flow for review. In the unsteady flow analysis the flow rate changed by $(-)0.16%{\sim}(+)0.26%$, and the flood elevation varied by $(-)0.35%{\sim}(+)0.51%$ as compared to the values in the steady flow analysis. Given these results, in the one-dimensional flow analysis based on the unsteady flow the flood elevation and flow rate were greater than when the analysis was done on the basis of the steady flow. The flow state was analyzed on the basis of the two-dimensional steady flow and unsteady flow. In the unsteady flow analysis the flow rate varied by $(-)0.16%{\sim}(+)1.08%$, and the flood elevation changed by $(-)0.24%{\sim}(+)0.41%$ as compared to the values in the steady flow analysis. Given these analysis results, in the two dimensional flow analysis based on the unsteady flow, the flood elevation and flow rate were greater than when the analysis was done on the basis of the steady flow.

A Study of Artificial Reef Subsidence in Unsteady Flow Field (비정상 흐름장의 인공어초 침하특성에 관한 실험적 연구)

  • 윤상준;김헌태
    • Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
    • /
    • /
    • pp.234-239
    • /
    • 2001
  • The subsidence characteristics of artificial reef in the unsteady flow such as tidal flow were investigated. The scour and subsidence characteristics were confirmed in the steady flow field, wave field and steady flow-wave field. In a main study, the interaction of Flow-Sediment Movement-Structure Behavior and scour.subsidence mechanism were discussed in the unsteady flow field and the unsteady flow-wave field. Most of all, the continuous artificial reef subsidence from the scour was occurred by periodic behavior of artificial reef. This behavior is result from the asymmetric ground, and is influenced by maximum velocity, duration time and direction of flow.

  • PDF

An Investigation of Flow Characteristics of Radial Gas Turbine for Turbocharger under Unsteady Flow (과급기용 Radial Turbine의 비정상 유동특성에 관한 연구)

  • Choi, J.S.;Koh, D.K.;Winterbone, D.E.
    • Transactions of the Korean Society of Automotive Engineers
    • /
    • v.2 no.2
    • /
    • pp.42-48
    • /
    • 1994
  • Turbocharging is one of the best methods to improve the performance of diesel engines, because of its merits,-power ratio, fuel consumption and exhaust emissions. Most of them in small and medium diesel engines have adopted the pulse turbocharging method with twin entry vaneless radial turbines to maximize the energy utility of exhaust gas. This method requires the high performance of turbine under unsteady flow, and also the matching between turbine and diesel engine is most important. However, it is difficult to match properly between them. Because the steady flow data are usually used for it. Accordingly, it is necessary to catch the characteristics of turbine performance correctly over the wide range of the operation conditions under unsteady flow. In this paper, the characteristics of turbine performance under unsteady flow are represented at varying conditions, such as inlet pressure amplitude, turbine speed and frequence.

  • PDF

Dam Failure and Unsteady Flow Analysis through Yeoncheon Dam Case(II) - Unsteady Flow Analysis of Downstream by Failure Scenarios - (연천댐 사례를 통한 댐 파괴 부정류해석 및 하류 영향 검토(II) -시나리오에 따른 댐 하류 부정류 해석 및 범랑특성 연구-)

  • Jang, Suk-Hwan
    • Journal of Environmental Science International
    • /
    • v.17 no.11
    • /
    • pp.1295-1305
    • /
    • 2008
  • This study aims at the analyze of unsteady downstream flow due to dam failure along dam failure scenario and applied to Yeoncheon Dam which was collapsed August 1st 1999, using HEC-RAS simulation model. The boundary conditions of this unsteady flow simulation are that dam failure arrival time could be at 02:45 a.m. August 1st 1999 and failure duration time could be also 30 minutes. Downstream 19.5 km from dam site was simulated for unsteady flow analysis in terms of dam failure and non-failure cases. For the parameter calibration, observed data of Jeonkok station were used and roughness coefficient was applied to simulation model. The result of the peak discharge difference was 2,696 to $1,745\;m^3/sec$ along the downstream between dam failure and non-failure and also peak elevation of water level showed meanly 0.6m difference. Those results of these studies show that dam failure scenarios for the unknown failure time and duration were rational because most results were coincident with observed records. And also those results and procedure could suggest how and when dam failure occurs and downstream unsteady flow analyzes.

Steady/unsteady Flow Analysis for Industrial Mixer (산업용 교반기 내부 정상/비정상 유동특성해석)

  • Chang, J.;Hur, N.
    • 유체기계공업학회:학술대회논문집
    • /
    • /
    • pp.460-465
    • /
    • 2001
  • In the present study, steady and unsteady flow characteristics inside an industrial mixer with flat turbine type impeller are studied. For the flow analysis, STAR-CD is used with an automatic mesh generator developed in the present study. flow results are compared to the an available experimental data to show validity or the present simulation.

  • PDF

A Study on Unsteady Flow measurement using Laser Doppler Velocimeter in Curved Duct (곡관에서 laser유속계를 이용한 비정상유동 계측에 대한 연구)

  • 조병기
    • Journal of Advanced Marine Engineering and Technology
    • /
    • v.20 no.4
    • /
    • pp.81-89
    • /
    • 1996
  • In the present study, the unsteady in a square-selctional 180.deg. curved duct are experimentally investigated. The experimental study using air in a square-sectional 180.deg. curved duct is carried out to measure axial velocity distributions with data acquisition and processing system. In this system, Rotating Machinery Resolver(RMR) and PHASE Software are used to obtain the results of unsteady flows. In conclusion, the exact measurement of unsteady flow using LDV system depends upon uniformity of metreials, duct thickness, and scattered particles.

  • PDF

Unsteady flow analysis of KSR-III pressurization system (KSR-III 가압 시스템에 대한 비정상 유동해석)

  • Jung T. K.;Jung Y. S.;Oh S. H.;Lee D. S.
    • 한국전산유체공학회:학술대회논문집
    • /
    • /
    • pp.116-120
    • /
    • 2001
  • The impactive Pressure wave induced by pyro valve in the pressurization system of KSR-III may result in fatal failure or malfunction of valves, so it is important to know the pressure wave characteristic in the pressurization system. An unsteady flow analysis in the simplified pressurization system was peformed by Finite difference method.

  • PDF