• Title/Summary/Keyword: Suction Surface

Search Result 304, Processing Time 0.024 seconds

Morphological Study of the Suction Trap in Aquatic Utricularia japonica (수생형 통발(Utricularia japonica)의 흡입식 포충낭 형태 연구)

  • Kim, In-Sun
    • Applied Microscopy
    • /
    • v.40 no.2
    • /
    • pp.109-116
    • /
    • 2010
  • Morphology and microstructure of the suction trap in aquatic Utricularia japonica were examined using scanning electron microscopy. Branched stems bear numerous suction traps without root formation. The traps are derived axillary from the node, and their antennae and appendages extend in a peculiar fashion. The trap walls are thin, two-celled, parenchyma tissue and simple, small glands are scattered in both internal and external surface of the trap. The entrance of the trap is surrounded by one pair of dorsal antennae and ventral appendages, where the former guides the prey to the entrance. Trap door is situated below the entrance and numerous sessile and stalked capitate trichomes cover the entrance and even on the door surface. The capitate trichomes are secretory, but four trigger hairs formed on the central areas of the door are not. They are believed to function in activating and tripping the trap door. A specialized region of the threshold come in contact with the lower portion of the door upon closing. The secretory capitate trichomes near this region are responsible for producing and secreting a mucilage-like substance which composes the velum. Two-armed bifid glands are located in the interior side of the threshold, while four-armed quadrifid glands are considerably numerous occurring over the entire inner trap wall. Bifid and quadrifid glands develop semi-spherical basal cells that connect them to the inner wall surface. Antennae, trigger hairs, capitate trichomes, bifid and quadrifid glands are more important structures in the carnivory of U. japonica.

Papers : Vortex Flow and Aerodynamic Load Characteristics of the Delta Wing / LEX Configuration in Sideslip (논문 : 옆미끄럼이 있는 삼각 날개 / LEX 형상의 와류와 공력 특성)

  • Son,Myeong-Hwan;Lee,Gi-Yeong;Baek,Seung-Uk
    • Journal of the Korean Society for Aeronautical & Space Sciences
    • /
    • v.30 no.3
    • /
    • pp.37-45
    • /
    • 2002
  • The vortex flow and aerodynamic load characteristics of a $65^{\circ}$ sweep delta wing with the leading edge extension in sideslip condition is investigated experimentally. The freestream velocity is 40 m/sec, which corresponds to a Reynolds number per meter of $1.76{\times}10^6$ based on the wing root chord. The angles of attack range from $12^{\circ}$ to $28^{\circ}$, and the sideslip angles treated are $0^{\circ}$ , $-10^{\circ}$, $-20^{\circ}$. The LEX vortex of the leeward side. The LEX and wing vortics coalesce to to become a concentrated strong vortex or to break down at down at downstream position. Due to the interation of the LEX and wing vortices, a high suction pressure is maintained on the windward wing surface, and a low suction pressure is formed on the leeward wing surface

The Numerical Simulation of Unsteady Flow in a Mixed flow Pump Guide Vane

  • Li, Yi-Bin;Li, Ren-Nian;Wang, Xiu-Yong
    • International Journal of Fluid Machinery and Systems
    • /
    • v.6 no.4
    • /
    • pp.200-205
    • /
    • 2013
  • In order to investigate the characteristics of unsteady flow in a mixed flow pump guide vane under the small flow conditions, several indicator points in a mixed flow pump guide vane was set, the three-dimensional unsteady turbulence numerical value of the mixed flow pump which is in the whole flow field will be calculated by means of the large eddy simulation (LES), sub-grid scale model and sliding mesh technology. The experimental results suggest that the large eddy simulation can estimate the positive slope characteristic of head & capacity curve. And the calculation results show that the pressure fluctuation coefficients of the middle section in guide vane inlet will decrease firstly and then increase. In guide vane outlet, the pressure fluctuation coefficients of section will be approximately axially symmetrical distribution. The pressure fluctuation minimum of section in guide vane inlet is above the middle location of the guide vane suction surface, and the pressure fluctuation minimum of section in which located the middle and outlet of guide vane. When it is under the small flow operating condition, the eddy scale of guide vane is larger, and the pressure fluctuation of the channel in guide vane being cyclical fluctuations obviously which leads to the area of eddy expanding to the whole channel from the suction side. The middle of the guide vane suction surface of the minimum amplitude pressure fluctuation to which the vortex core of eddy scale whose direction of fluid's rotation is the same to impeller in the guide vane adhere.

Geometrical Design and SLIPS Lubrication for Enhancement of Negative-pressure-driven Internal Flow Rate in Metal Pipes (금속관 내부의 음압유량 향상을 위한 기하학적 디자인 및 SLIPS 윤활)

  • Kim, Dong Geun;Jang, Changhwan;Kim, Seong Jae;Kim, Daegyoum;Kim, Sanha
    • Tribology and Lubricants
    • /
    • v.37 no.6
    • /
    • pp.253-260
    • /
    • 2021
  • Metal pipes are used in a wide range of applications, from plumbing systems of large construction sites to small devices such as medical tools. When a liquid is enforced to flow through a metal pipe, a higher flow rate is beneficial for higher efficiency. Using high pressures can enhance the flow rate yet can be harmful for medical applications. Thus, we consider an optimal geometrical design to increase the flow rate in medical devices. In this study, we focus on cannulas, which are widely used small metal pipes for surgical procedures, such as liposuction. We characterize the internal flow rate driven by a negative pressure and explore its dependence on the key design parameters. We quantitatively analyze the suction characteristics for each design variable by conducting computational fluid dynamics simulations. In addition, we build a suction performance measurement system which enables the translational motion of cannulas with pre-programmed velocity for experimental validation. The inner diameter, section geometry, and hole configuration are the design factors to be evaluated. The effect of the inner diameter dominates over that of section geometry and hole configuration. In addition, the circular tube shape provides the maximum flow rate among the elliptical geometries. Once the flow rate exceeds a critical value, the rate becomes independent of the number and width of the suction holes. Finally, we introduce a slippery liquid-infused nanoporous surface (SLIPS) coating using nanoparticles and hydrophobic lubricants that effectively improves the flow rate and antifouling property of cannulas without altering the geometrical design parameter.

Silicon/Pad Pressure Measurements During Chemical Mechanical Polishing

  • Danyluk, Steven;Ng, Gary;Yoon, In-Ho;Higgs, Fred;Zhou, Chun-Hong
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
    • /
    • 2002.10b
    • /
    • pp.433-434
    • /
    • 2002
  • Chemical mechanical polishing refers to a process by which silicon and partially-processed integrated circuits (IC's) built on silicon substrates are polished to produce planar surfaces for the continued manufacturing of IC's. Chemical mechanical polishing is done by pressing the silicon wafer, face down, onto a rotating platen that is covered by a rough polyurethane pad. During rotation, the pad is flooded with a slurry that contains nanoscale particles. The pad deforms and the roughness of the surface entrains the slurry into the interface. The asperities contact the wafer and the surface is polished in a three-body abrasion process. The contact of the wafer with the 'soft' pad produces a unique elastohydrodynamic situation in which a suction force is imposed at the interface. This added force is non-uniform and can be on the order of the applied pressure on the wafer. We have measured the magnitude and spatial distribution of this suction force. This force will be described within the context of a model of the sliding of hard surfaces on soft substrates.

  • PDF

Dynamic Behavior of Vortices Separated from a Pitching Foil (피칭익에서 박리되는 와류의 거동)

  • Yang, Chang-Jo
    • Journal of Advanced Marine Engineering and Technology
    • /
    • v.31 no.2
    • /
    • pp.152-158
    • /
    • 2007
  • Most of experimental visualizations and numerical results on the flow field separated form a leading edge around an unsteady foil show a continuous streakline from the leading edge and large reverse flow between the streakline and the suction surface. However, they have not exactly clarified yet the dynamic behavior of vortices separated from the leading edge because separation around an unsteady foil is very complicated phenomenon due to many parameters. In the present study the flow fields around pitching foils have been visualized by using a Schlieren method with a high speed camera in a wind tunnel at low Reynolds number regions. It has been observed that small vortices are shed discretely from the leading and trailing edge and that they stand in line on the integrated streakline of separation shear layer. By counting vortices in the VTR frames it was clarified that the number of vortex shedding from the leading and trailing edge during one pitching cycle strongly depends on the non-dimensional pitching rate. Futhermore the vortices moving up to the leading edge on the suction surface of the pitching foil are visualized. They play an important role to balance the number of vortex shedding from both edges.

Experimental Study on the Heat Transfer under the Effects of Wake In a Turbine Cascade (후류의 영향을 고려한 터빈 캐스케이드내 열전달 현상에 대한 실험적 연구)

  • Min, H.K.;Chung, J.T.
    • Proceedings of the KSME Conference
    • /
    • 2001.11b
    • /
    • pp.36-41
    • /
    • 2001
  • In order to simulate wake of stator and a gas turbine engine's balde row, acryl cylinder and a linear turbine cascade were used respectively in this study. Experimental of heat transfer distributions was done on the passage endwall and blade suction surface. Temperature distributions on the experimental regions were obtained through image processing system by using the cholesteric type liquid crystal which has chain structure of metyl$(CH_3)$. To represent the degree of heat transfer, dimensionless St number was used. The results show that heat transfer on the blade suction surface was increased due to the wake from the cylinder and was decreased as the distance between cylinder row and blade row increases. Because of groth of passage vortex, heat transfer distributions on the trailing edge area showed triangular shape which was little changed with wake. On the other hand, heat transfer on the passage endwall was decreased due to the wake from cylinder. As the distance between cylinder row and blade row increases, heat transfer was more decreased.

  • PDF

Effects of Reynolds Number on Flow and Heat/Mass Characteristics Inside the Wavy Duct (Reynolds 수에 따른 꺾어진 덕트에서 열/물질전달 특성 고찰)

  • 장인혁;황상동;조형희
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
    • /
    • v.15 no.10
    • /
    • pp.809-820
    • /
    • 2003
  • The present study investigates effects of flow velocity on the convective heat/mass transfer characteristics in wavy ducts of a primary surface heat exchanger application. Local heat/mass transfer coefficients on the wavy duct sidewall are determined by using a naphthalene sublimation technique. The flow visualization technique is used to understand the overall flow structures inside the duct. The aspect ratio and corrugation angle of the wavy duct is fixed at 7.3 and 145$^{\circ}$ respectively, and the Reynolds numbers, based on the duct hydraulic diameter, vary from 100 to 5,000. The results show that there exist complex secondary flows and transfer processes resulting in non-uniform distributions of the heat/mass transfer coefficients on the duct side walls. At low Re (Re<1000), relatively high heat/mass transfer regions like cell shape appear on both pressure and suction side wall due to the secondary vortex flows called Taylor-Gortler vortices perpendicular to the main flow direction. However, at high Re (Re>1000), these secondary flow cells disappear and boundary layer type flow characteristics are observed on pressure side wall and high heat/mass transfer region by the flow reattachment appears on the suction side wall. The average heat/mass transfer coefficients are higher than those of the smooth circular duct due to the secondary flows inside wavy duct. And also friction factors are about two times greater than those of the smooth circular duct.

Study on the Generation of Turbulent Boundary Layer in Wind Tunnel and the Effect of Aspect Ratio of a Rectangular Obstacle (풍동 내 난류 경계층 생성과 육면체의 형상 변화에 따른 표면 압력 변화 연구)

  • LimM, Hee-Chang;Jeong, Tae-Yoon
    • Transactions of the Korean Society of Mechanical Engineers B
    • /
    • v.32 no.10
    • /
    • pp.791-799
    • /
    • 2008
  • We investigate the flow characteristics around a series of rectangular bodies ($40^d{\times}80^w{\times}80^h$, $80^d{\times}80^w{\times}80^h$ and $160^d{\times}80^w{\times}80^h$) placed in a deep turbulent boundary layer. The study is aiming to understand the surface pressure distribution around the bodies such as the suction pressure in the leading edge, when the flow is normal, which is responsible for producing extreme suction pressures on the roof. The experiment includes wind tunnel work by using HWA (Hot-Wire anemometry) and pressure transducers. The experiments are carried out at three different Reynolds numbers, based on the velocity U at the body height h, of $2.4{\times}10^4$, $4.6{\times}10^4$ and $6.7{\times}10^4$, and large enough that the mean flow is effectively Reynolds number independent. The results include the measurements of the growth of the turbulent boundary layer in the wind tunnel and the surface pressure around the bodies.

A Study on Rainfall Induced Slope Failures: Implications for Various Steep Slope Inclinations

  • Do, Xuan Khanh;Jung, Kwansue;Lee, Giha;Regmi, Ram Krishna
    • Journal of the Korean GEO-environmental Society
    • /
    • v.17 no.5
    • /
    • pp.5-16
    • /
    • 2016
  • A rainfall induced slope failure is a common natural hazard in mountainous areas worldwide. Sudden and rapid failures which have a high possibility of occurrence in a steep slope are always the most dangerous due to their suddenness and high velocities. Based on a series of experiments this study aimed to determine a critical angle which could be considered as an approximate threshold for a sudden failure. The experiments were performed using 0.42 mm mean grain size sand in a 200 cm long, 60 cm wide and 50 cm deep rectangular flume. A numerical model was created by integrating a 2D seepage flow model and a 2D slope stability analysis model to predict the failure surface and the time of occurrence. The results showed that, the failure mode for the entire material will be sudden for slopes greater than $67^{\circ}$; in contrast the failure mode becomes retrogressive. There is no clear link between the degree of saturation and the mode of failure. The simulation results in considering matric suction showed good matching with the results obtained from experiment. A subsequent discarding of the matric suction effect in calculating safety factors will result in a deeper predicted failure surface and an incorrect predicted time of occurrence.