• Title/Summary/Keyword: flow angle

Search Result 2,897, Processing Time 0.037 seconds

Physics-based modelling for a closed form solution for flow angle estimation

  • Lerro, Angelo
    • Advances in aircraft and spacecraft science
    • /
    • v.8 no.4
    • /
    • pp.273-287
    • /
    • 2021
  • Model-based, data-driven and physics-based approaches represent the state-of-the-art techniques to estimate the aircraft flow angles, angle-of-attack and angle-of-sideslip, in avionics. Thanks to sensor fusion techniques, a synthetic sensor is able to provide estimation of flow angles without any dedicated physical sensors. The work deals with a physics-based scheme derived from flight mechanic theory that leads to a nonlinear flow angle model. Even though several solvers can be adopted, nonlinear models can be replaced with less accurate but straightforward ones in practical applications. The present work proposes a linearisation to obtain the flow angles' closed form solution that is verified using a flight simulator. The main objective of the paper, in fact, is to analyse the estimation degradation using the proposed closed form solutions with respect to the nonlinear scheme. Moreover, flight conditions, where the proposed closed form solutions are not applicable, are identified.

Flow past a Square Cylinder with an Angle of Attack (기울어진 정방형 실린더에 작용하는 유체력)

  • Yoon, Dong-Hyeog;Yang, Kyung-Soo;Choi, Choon-Bum
    • Proceedings of the KSME Conference
    • /
    • 2008.11b
    • /
    • pp.2754-2758
    • /
    • 2008
  • Numerical investigation has been carried out for laminar flow ($Re{\leq}150$) past a square cylinder in cross freestream with an angle of attack. This study would be the first step towards understanding flow-induced forces on cylindrical structures under a strong gust of wind from the viewpoint of wind hazards. Collecting all the numerical results obtained, we propose contour diagrams of drag/lift coefficients and Strouhal number (St) on an Re-Angle plane.

  • PDF

Optimal Flow Control of Ceiling Type Indoor Unit by PIV Measurements (PIV 유동 계측을 통한 천장형 실내기의 최적 제어 설계)

  • Sung, Jae-Yong;An, Kwang-Hyup;Lee, Gi-Seop;Choi, Ho-Seon;Lee, In-Seop
    • Transactions of the Korean Society of Mechanical Engineers B
    • /
    • v.27 no.8
    • /
    • pp.1042-1050
    • /
    • 2003
  • A heating flow discharged from a 4-way ceiling type indoor unit has been investigated to determine the design parameters for the optimal flow control. The flow was measured by a PIV(particle image velocimetry) system and an experimental model of 1/10 scale with a transparent room was devised by satisfying the Archimedes number. This similarity is generally used in cases where the forced convection has similar magnitude of the natural convection. To optimize the heating flow, several vane angles and vane control algorithms of cross and right angle controls were considered. Regarding the vane angle, experimental results show that 30$^{\circ}$is an optimal angle to avoid re-suction flows without significant increase in flow noise. Temperature distribution measured in the environmental chamber ensures the increased thermal comfort when compared to the case, 60$^{\circ}$angle. At the optimal angle, applying open/close control gives rise to more uniform distribution of the heating flow than without control. Especially, the cross-control seems to be satisfactory for thermal comfort.

Thruster Modeling for Underwater Vehicle with Ambient Flow Velocity and its Incoming Angle (외부 유체의 영향을 고려한 무인잠수정의 추진기 모델)

  • Kim, Jin-Hyun;Chung, Wan-Kyun
    • The Journal of Korea Robotics Society
    • /
    • v.2 no.2
    • /
    • pp.109-118
    • /
    • 2007
  • The thruster is the crucial factor of an underwater vehicle system, because it is the lowest layer in the control loop of the system. In this paper, we propose an accurate and practical thrust modeling for underwater vehicles which considers the effects of ambient flow velocity and angle. In this model, the axial flow velocity of the thruster, which is non-measurable, is represented by ambient flow velocity and propeller shaft velocity. Hence, contrary to previous models, the proposed model is practical since it uses only measurable states. Next, the whole thrust map is divided into three states according to the state of ambient flow and propeller shaft velocity, and one of the borders of the states is defined as Critical Advance Ratio (CAR). This classification explains the physical phenomenon of conventional experimental thrust maps. In addition, the effect of the incoming angle of ambient flow is analyzed, and Critical Incoming Angle (CIA) is also defined to describe the thrust force states. The proposed model is evaluated by comparing experimental data with numerical model simulation data, and it accurately covers overall flow conditions within 2N force error. The comparison results show that the new model's matching performance is significantly better than conventional models'.

  • PDF

Experimental Study on the Surface Pressure Characteristics of a Rear-Guider for the Various Design Factors of a Cross-Flow Fan (관류홴의 설계인자 변화에 따른 리어가이더의 표면압력 특성에 관한 실험적 연구)

  • Kim, J.K.
    • Journal of Power System Engineering
    • /
    • v.9 no.3
    • /
    • pp.50-57
    • /
    • 2005
  • A cross-flow fan is strongly influenced by the various design factors of a rear-guider and a stabilizer. The purpose of this paper is to investigate the effects of a rear-guider and a stabilizer on the surface pressure of a rear-guider in an indoor room air-conditioner using a cross-flow fan. The design factors considered in this paper are a rear-guider clearance, a stabilizer clearance, and a stabilizer setup angle, respectively. The operating condition of a cross-flow fan was controlled by changing the static pressure and flowrate using a fan tester. All surface pressures of a rear-guider are differently distributed according to the stabilizer setup angle, and show a zero value in the flow coefficient, ${\Phi}{\fallingdotseq}0.5$ only of a stabilizer setup angle, $45^{\circ}$. Especially, they show a big negative value in the expansion angle larger than $34^{\circ}$ regardless of a rear-guider clearance, a stabilizer clearance, and a stabilizer setup angle. On the other hand, surface pressures for various stabilizer cutoff clearances are better than those for various rear-guider clearances.

  • PDF

The Study of Aliasing and Incidence Angle Dependence of Doppler Image on Humeral Artery (상완동맥 Doppler 영상의 입사각 의존성과 Aliasing에 관한 연구)

  • Kim, Sang-Jin;Ji, Tae-Jeong
    • Journal of radiological science and technology
    • /
    • v.31 no.4
    • /
    • pp.379-387
    • /
    • 2008
  • Among methods to eliminate aliasing effects, the method of increasing velocity scale gradually eliminated the phenomenon in which the direction of the blood flow appeared in reverse. It was done by increasing the velocity scale while maintaining other parameters in the same state. The method of setting the Doppler angle to $0^{\circ}$ did not show significant changes in the wave pattern of the spectrum according to the angle. In actual ultrasonography tests, more accurate tests are expected to be carried out by applying variations to the velocity scale under the considerations of speed, accuracy, and convenience of the examination. The results showed that blood flow velocity increases exponentially according to the Doppler Angle. When the angle goes over $70^{\circ}$, the velocity value increases to an unmeasurable state. This indicates that in blood flow velocity measurements, the blood flow velocity is very dependent on the Doppler Angle. It also shows that the error increases when the incidence angle to the direction of blood flow exceeds $60^{\circ}$, and when the angle exceeds $70^{\circ}$, the error becomes even greater. In addition, he experiment results showed that an angle below $60^{\circ}$ is appropriate and for blood flow velocity measurements in extremity vessels, the most appropriate Doppler Angle is from $45^{\circ}$ to $60^{\circ}$.

  • PDF

Numerical Simulation for Behavior of Debris Flow according to the Variances of Slope Angle (비탈면 경사 변화에 따른 토석류 거동의 수치모의)

  • Kim, Sungduk;Yoon, Ilro;Oh, Sewook;Lee, Hojin;Bae, Wooseok
    • Journal of the Korean GEO-environmental Society
    • /
    • v.13 no.6
    • /
    • pp.59-66
    • /
    • 2012
  • The purpose of this study is to estimate the behavior and the mechanism of debris flow on the slope, which has specially various gradient plane. The numerical simulation was performed by using the Finite Differential Element method (FDM) based on the equation for the mass conservation and momentum conservation. The mechanism of flow type for debris flow is divided into three flow types which are stony debris flow, immature debris flow, and turbulent water flow, respectively. First, flow discharge, water flow depth, sediment volume concentration was investigated by variable input of flow discharge at the straight slope angle and two step inclined plane. As the input of flow discharge was decrease, flow discharge and water flow depth was increased, after the first coming debris flow only reached at the downstream. As the input of flow discharge was increased, the curve of flow discharge and flow depth was highly fluctuated. As the results of RMS ratio, the flow discharge and flow depth was lower two step slope angle than the straight slope angle. Second, the behavior of debris flow was investigated by the four cases of gradient degree at the downstream of slope angle. The band width of flow discharge and flow depth for $14^{\circ}$ between $16^{\circ}$ was higher than other gradient degree, and fluctuation curve was continuously high after 10 seconds.

The Effect of Water Contact Angles of the Fin Surfaces of the Fin-and-Tube Heat Exchangers on the Water Hold-up (핀-관 열교환기에서의 핀의 물 접촉각이 응축잔수량에 미치는 영향)

  • 신종민;이남교;한성주;하삼철
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
    • /
    • v.13 no.6
    • /
    • pp.490-496
    • /
    • 2001
  • An experimental study on the behavior of the water hold-up by condensation of a fin-and-tube heat exchanger with regard to the surface characteristics, i.e., contact angle, was conducted. The static and dynamic contact angles were measured, and condensation experiments were conducted. Flow patterns on the fins with different surface characteristics were visualized. Results showed that the static contact angle is proportional to the dynamic contact angle within the range of this study. The water hold-up of the heat exchanger increases as the static or dynamic contact angle of its surfaces increases. Existence of transition of flow patterns was found as the static or dynamic angle increase. Due to the transition in the flow patterns, changes in the gradient of the water hold-up is occurred around the static angle of 8$0^{\circ}C$.

  • PDF

Effect of Incidence Angle on Turbine Blade Heat Transfer Characteristics (II) - Blade Surface - (입사각 변화에 따른 터빈 블레이드에서의 열전달 특성 변화 (II) - 블레이드 표면 -)

  • Rhee, Dong-Ho;Cho, Hyung-Hee
    • Transactions of the Korean Society of Mechanical Engineers B
    • /
    • v.31 no.4
    • /
    • pp.357-366
    • /
    • 2007
  • The present study investigated local heat/mass transfer characteristics on the surface of the rotating turbine blade with various incidence angles. The experiments are conducted in a low speed annular cascade with a single stage turbine. The blade has a flat tip with the mean tip clearance of 2.5% of the blade chord. A naphthalene sublimation method is used to measure detailed mass transfer coefficient on the blade. At design condition, the inlet Reynolds number is $Re_c=1.5{\times}10^5$ which results in the blade rotation speed of 255.8 rpm. Also, the effect of off-design condition is examined with various incidence angles between $-15^{\circ}$ and $+7{\circ}$. The results indicated that the incidence angle has significant effects on the blade surface heat transfer. In mid-span region, the laminar separation region on the pressure side is reduced and the laminar flow region on the suction side shrinks with increasing incidence angle. Near the tip, the effect of tip leakage flow increases in span wise and axial directions as the incidence angle decreases because the tip leakage flow is formed near the suction side surface. However, the effect of tip leakage flow is reduced with positive incidence angle.

Large viewing angle walk through type display using smoke screen

  • Sato, Koki;Takano, Kunihiko;Ohki, Makoto
    • Proceedings of the Korean Society of Broadcast Engineers Conference
    • /
    • 2009.01a
    • /
    • pp.790-793
    • /
    • 2009
  • In the case of projection type display, it needs to use the screen in order to project the image clearly and wide viewing angle. We have been developing the step in type display system using the smoke screen. However, the image with smoke screen was flickered by gravity and air flow. Then we considered to reduce the flicker of the image and we found that flicker can be reduced and viewing angle becomes more large. This time we report the large viewing angle step in type display system using screen made up with very small particle size smoke and flow controlled nozzle. Hence, at first we considered the most suitable particle for the screen and then the shape of screen and then we constructed the array of flow controlled smoke screen. By the results of experiment we could get considerably high contrast flicker-less image and get the viewing angle more than $60^{\circ}$ by this flow controlled nozzle attached new type smoke screen and make clear the efficiency of this method.

  • PDF