An Extended Linearized Inverse Theory for Fully Cavitating Hydrofoil Section Design

1979 ◽  
Vol 23 (04) ◽  
pp. 260-271
Author(s):  
Blaine R. Parkin ◽  
Joe Fernandez
Keyword(s):  
Design Theory ◽  
Parametric Design ◽  
Lift Coefficient ◽  
Design Procedure ◽  
Cavitation Number ◽  
Inverse Theory ◽  
Cavity Surface ◽  
Moment Coefficient ◽  
Section Design ◽  
Cavity Thickness

A new design theory for fully cavitating hydrofoils is based upon a linearized inverse theory of two-dimensional cavity flows at arbitrary cavitation number. The cavity surfaces are assumed to originate at the leading and trailing edges of the wetted surface. This paper reviews and completes the basic theory, which leads to a parametric design technique. In the resulting design procedure, one specifies the design lift coefficient, the cavitation number and the upper cavity thickness at two points along the profile chord. A prescribed pressure distribution shape is also selected. These quantities determine the profilelesgn, which consists of the upper cavity and wetted surface contours, the design angle of attack, the cavity length, the drag coefficient, the moment coefficient and the lift-to-drag ratio. The chief new feature of the third design procedure is that the designer can now prescribe two points on the cavity surface instead of one as heretofore. Although the designer must observe certain constraints when he specifies these two values of cavity thickness, the new procedure is still found to be more general and more flexible than design procedures studied previously.

Hydrodynamic Trends from a Generalized Design Procedure for Fully Cavitating Hydrofoil Sections

1979 ◽  
Vol 23 (04) ◽  
pp. 272-283
Author(s):  
Blaine R. Parkin ◽  
Joe Fernandez
Keyword(s):  
Parametric Design ◽  
Lift Coefficient ◽  
Design Procedure ◽  
Feasibility Studies ◽  
Cavitation Number ◽  
Hydrodynamic Performance ◽  
Cavity Surface ◽  
Cavity Flows ◽  
Moment Coefficient ◽  
Cavity Thickness

An extended design procedure for fully cavitating hydrofoils is based upon a linearized inverse theory of two-dimensional cavity flows at arbitrary cavitation number. The cavity surfaces are assumed to originate at the leading and trailing edges of the wetted surface. This paper completes the basic theory and gives detailed examples obtained from the resulting parametric design technique. In this procedure, one specifies the design lift coefficient, the cavitation number and the upper cavity thickness at two points along the profile chord. A prescribed pressure distribution shape is also selected. These quantities determine the profile design, which consists of the upper cavity and wetted surface contours, the design angle of attack, the cavity length, the drag coefficient, the moment coefficient and the lift-to-drag ratio. The method also includes off-design calculations in accordance with the direct theory of cavity flows, which determines the flow states for which interference can occur between the upper surface of the cavity and the upper nonwetted surface of the profile. The hydrodynamic performance of specific "point designs" is also given by these direct calculations. The chief new feature of the generalized design procedure is that it gives a designer the ability to prescribe two points on the cavity surface instead of one as heretofore. Although certain constraints must be observed by the designer when specifying these two values of cavity thickness, the third procedure is found to be more general and more flexible than design procedures studied previously. The necessary constraints are incorporated in the computer logic for the method. The fact that linearized theory is used tends to limit the applicability of the method to conceptual design and feasibility studies. The computer program for the procedure has been found to be economical and well suited for its intended purpose.

scholarly journals Dynamics of Attached Cavities on Bodies of Revolution

1992 ◽  
Vol 114 (1) ◽  
pp. 93-99 ◽  
Author(s):  
S. L. Ceccio ◽  
C. E. Brennen
Keyword(s):  
Reynolds Numbers ◽  
Cavitation Number ◽  
The Body ◽  
Cavity Surface ◽  
Bodies Of Revolution ◽  
The Mean ◽  
Cavity Thickness ◽  
Cavity Closure ◽  
Axisymmetric Bodies ◽  
Single Cavity

Attached cavitation was generated on two axisymmetric bodies, a Schiebe body and a modified ellipsoidal body (the I. T. T. C. body), both with a 50.8 mm diameter. Tests were conducted for a range of cavitation numbers and for Reynolds numbers in the range of Re = 4.4 × 105 to 4.8 × 105. Partially stable cavities were observed. The steady and dynamic volume fluctuations of the cavities were recorded through measurements of the local fluid impedance near the cavitating surface suing a series of flush mounted electrodes. These data were combined with photographic observations. On the Schiebe body, the cavitation was observed to form a series of incipient spot cavities which developed into a single cavity as the cavitation number was lowered. The incipient cavities were observed to fluctuate at distinct frequencies. Cavities on the I. T. T. C. started as a single patch on the upper surface of the body which grew to envelope the entire circumference of the body as the cavitation number was lowered. These cavities also fluctuated at distinct frequencies associated with oscillations of the cavity closure region. The cavities fluctuated with Strouhal numbers (based on the mean cavity thickness) in the range of St = 0.002 to 0.02, which are approximately one tenth the value of Strouhal numbers associated with Ka´rma´n vortex shedding. The fluctuation of these stabilized partial cavities may be related to periodic break off and filling in the cavity closure region and to periodic entrainment of the cavity vapor. Cavities on both headforms exhibited surface striations in the streamwise direction near the point of cavity formation, and a frothy mixture of vapor and liquid was detected under the turbulent cavity surface. As the cavities became fully developed, the signal generated by the frothy mixture increased in magnitude with frequencies in the range of 0 to 50 Hz.

Supercavitating Foils With Flaps Beneath a Free Surface

1964 ◽  
Vol 86 (2) ◽  
pp. 197-204
Author(s):  
J. Auslaender
Keyword(s):  
Free Surface ◽  
Lift Coefficient ◽  
Angle Of Attack ◽  
Cavitation Number ◽  
Operating Conditions ◽  
Mapping Technique ◽  
Moment Coefficient ◽  
Lift Curve ◽  
Flap Deflection ◽  
Drag Ratio

Linearized airfoil theory—in conjunction with a mapping technique—is applied to the calculation of the forces and moments acting on supercavitating hydrofoils operating near a free surface at very large Froude numbers and zero cavitation number. Only the effects of angle of attack and flap deflection are considered. The results—intended for engineering use—are presented primarily in the form of curves of flap effectiveness, lift curve slope, pitching and hinge moment coefficient, and flap loading versus flap-chord ratio, depth being introduced as a parameter. Lift-drag ratio and hinge moment coefficient as functions of lift coefficient are presented for typical operating conditions.

Hydrodynamic Trends for Preliminary Design of Fully Cavitating Hydrofoil Sections

1977 ◽  
Vol 14 (01) ◽  
pp. 70-85
Author(s):  
Blaine R. Parkin ◽  
Robert F. Davis ◽  
Joseph Fernandez
Keyword(s):  
Pressure Distribution ◽  
Lift Coefficient ◽  
Flow Theory ◽  
Cavity Flow ◽  
Cavitation Number ◽  
Viscous Drag ◽  
Preliminary Design ◽  
Two Dimensional ◽  
Cavity Thickness ◽  
Cavitating Hydrofoil

The object of this numerical study is to consider possible hydrodynamic trends for use in trade-off studies for the preliminary design of fully cavitating hydrofoil sections. Hydrodynamic data are obtained from inverse calculations which are based upon two-dimensional linearized cavity-flow theory. Supplementary data are also calculated from the direct problem of linearized cavity-flow theory in order to show off-design performance trends and to assess the effects of cavity-foil interference on the operating range of selected profiles. For the inverse calculations one specifies design values of the lift coefficient, cavitation number, and cavity thickness at the trailing edge, as well as the shape of the pressure distribution on the wetted surface of the hydrofoil section. In accordance with this specification, the ordinates of the profile wetted surface and upper-cavity contour are calculated, together with values of drag coefficient, moment coefficient, and attack angle at the design point. The paper summarizes the results of a parametric study of the effects of design cavitation number, lift coefficient, cavity thickness, and pressure distribution shape upon hydrofoil section performance and geometry. Three-dimensional wing effects, viscous drag, and the effects of structural design criteria are all outside the scope of the study. Results pertaining to steady two-dimensional cavity flows of an ideal incompressible fluid past a rigid hydrofoil section are presented.

Hydrofoil Drag Reduction by Partial Cavitation

2006 ◽  
Vol 128 (5) ◽  
pp. 931-936 ◽  
Author(s):  
Eduard Amromin ◽  
Jim Kopriva ◽  
Roger E. A. Arndt ◽  
Martin Wosnik
Keyword(s):  
Drag Reduction ◽  
Lift Coefficient ◽  
Design Procedure ◽  
Suction Side ◽  
Operating Regime ◽  
Cavitation Number ◽  
Partial Cavitation ◽  
Lift And Drag ◽  
Naca 0015 ◽  
Drag Ratio

Partial cavitation reduces hydrofoil friction, but a drag penalty associated with unsteady cavity dynamics usually occurs. With the aid of inviscid theory a design procedure is developed to suppress cavity oscillations. It is demonstrated that it is possible to suppress these oscillations in some range of lift coefficient and cavitation number. A candidate hydrofoil, denoted as OK-2003, was designed by modification of the suction side of a conventional NACA-0015 hydrofoil to provide stable drag reduction by partial cavitation. Validation of the design concept with water tunnel experiments has shown that the partial cavitation on the suction side of the hydrofoil OK-2003 does lead to drag reduction and a significant increase in the lift to drag ratio within a certain range of cavitation number and within a three-degree range of angle of attack. Within this operating regime, fluctuations of lift and drag decrease down to levels inherent to cavitation-free flow. The favorable characteristics of the OK-2003 are compared with the characteristics of the NACA-0015 under cavitating conditions.

Explanation of the Influence of Inflow Air Content on the Lift of Cavitating Hydrofoils

2018 ◽  
Vol 140 (8) ◽  
Author(s):  
Eduard Amromin
Keyword(s):  
Experimental Data ◽  
Theoretical Study ◽  
Lift Coefficient ◽  
Cavity Surface ◽  
Air Bubbles ◽  
Incoming Flow ◽  
Fluid Density ◽  
Air Content ◽  
Theoretical Results ◽  
Good Agreement

According to several known experiments, an increase of the incoming flow air content can increase the hydrofoil lift coefficient. The presented theoretical study shows that such increase is associated with the decrease of the fluid density at the cavity surface. This decrease is caused by entrainment of air bubbles to the cavity from the surrounding flow. The theoretical results based on such explanation are in a good agreement with the earlier published experimental data for NACA0015.

Parametric Design of Parts in an Integrated Simulation System Based on Asynchronous Mode of Pro/TOOLKIT

2012 ◽  
Vol 479-481 ◽  
pp. 1403-1408
Author(s):  
Gang Lian Zhao ◽  
Yi Jiang ◽  
Yu Jun Chen ◽  
Yan Li Ma
Keyword(s):  
Binary Tree ◽  
Parametric Design ◽  
Design Procedure ◽  
Simulation System ◽  
Tree Structure ◽  
Asynchronous Mode ◽  
Engineering Drawing ◽  
Integrated Simulation ◽  
Binary Tree Structure ◽  
Different Parts

Based on software Pro/ENGINEER and Visual C++ 2005，sub-module of parametric design of assembly with wide universality was done by using Pro/TOOLKIT, and the design procedure was introduced in details. Assembly relation of sub-components is transformed into binary tree structure to store and search parts, and the assembly relation is displayed by CTreeCtrl control. The corresponding parts can be quickly found in the binary tree. Engineering drawing was automatically generated and displayed by ProductView after loading a part, and in this way dimensions of different parts can be modified according to engineering drawing in asynchronous mode. The sub-module can meet the needs of parametric design of parts in the integrated simulation system.

BACKSTEPPING CONTROL OF NONLINEAR ROLL MOTION FOR A TRAWLER WITH FIN STABILIZER

2021 ◽  
Vol 159 (A2) ◽  
Author(s):  
H Demirel ◽  
A Doğrul ◽  
S Sezen ◽  
F Alarçin
Keyword(s):  
Lift Coefficient ◽  
Design Procedure ◽  
Nonlinear Damping ◽  
Backstepping Control ◽  
Roll Motion ◽  
Scaled Model ◽  
3 Dimensional ◽  
Roll Control ◽  
Fin Stabilizer ◽  
Volume Method

A backstepping control design procedure for nonlinear fin roll control of a trawler is presented in this paper. A roll equation consisting of linear and nonlinear damping and restoring moment on the roll response is expressed. Flow analyses are carried out for a scaled model of trawler type fishing vessel including fin stabilizers on both sides of the hull. The fin stabilizer geometry is chosen as NACA 0015 foil section which is widely used in the literature. The flow analyses are performed by using a commercial computational fluid dynamics (CFD) software based on finite volume method. The flow problem is modeled in a 3-dimensional manner while the flow is considered as steady, incompressible and fully turbulent. The numerical model consists of the ship wetted surface and the fin stabilizer in order to investigate the hull-fin interaction. Non-dimensional lift coefficients of the fin stabilizer for different angles of attack are gained. Both controlled and uncontrolled roll motions are examined and simulated in time domain for the maximum lift coefficient. Backstepping controller for roll motion has given a rapid and precise result.

Cognitive Challenges for Teamwork in Design

2017 ◽  
pp. 55-75 ◽  
Author(s):  
Ju Hyun Lee ◽  
Michael J. Ostwald ◽  
Ning Gu
Keyword(s):  
Experimental Data ◽  
Design Theory ◽  
Spatial Representation ◽  
Parametric Design ◽  
Design Strategy ◽  
Design Teams ◽  
Design Cognition ◽  
Cognitive Space ◽  
Design Experiments ◽  
Cognitive Challenges

This chapter combines experimental data and established design theory to examine four issues associated with design cognition that contribute to an improved understanding of creativity and teamwork in design. Drawing on data developed from two parametric design experiments undertaken by the authors, this chapter investigates the implications of (i) cognitive space, (ii) design strategy, (iii) design productivity and (iv) spatial representation, for individuals, and by inference, for groups and educators. Through this process the chapter develops a deeper understanding of the cognitive challenges facing design teams and educators of those teams.

scholarly journals Experimental Investigation of the Ground Effect of WIG Craft—NEW1 Model

Proceedings ◽  
2020 ◽  
Vol 39 (1) ◽  
pp. 17
Author(s):  
Sakornsin ◽  
Thipyopas ◽  
Atipan
Keyword(s):  
Lift Coefficient ◽  
Ground Surface ◽  
Ground Effect ◽  
Aerodynamic Characteristics ◽  
Scale Model ◽  
Negative Slope ◽  
Stream Velocity ◽  
Longitudinal Stability ◽  
Moment Coefficient ◽  
The Moment

Navy Experimental Wing-in-Ground-Effect (WIG) craft namely as NEW1, is the first version of 2-seated WIG craft which has been designed and developed by Royal Thai Navy since 2017. This experimental research is a part of the NEW1 project which aims to investigate the aerodynamic characteristics and aspects of the flow passing through the WIG craft model when in ground effect. In the experiment, the WIG craft—NEW1 of 1:15 scale model is tested in a close circuit wind tunnel of 1 m × 1 m test section at Kasetsart University. The tests are conducted at the free stream velocity of 40 m/s or Reynolds number of 280,000, at angles of attack ranging from −9° to 21°, and at the wing to ground distances ranging from 5.0 C to 0.3 C. The measurement of 6-DoF of forces and moments and pressure distributions on the ground surface underneath the WIG craft model are made during the tests. The results show that the ground has significant effects on the aerodynamic characteristics of the WIG craft model when the wing to ground distance is less than its mean chord. It was found that when the model move from 5.0 C (out of ground effect) to 0.3 C, the lift coefficient increases up to 15.7%, the drag coefficient decreases up to 5.6%, and the lift to drag ratio increases 33.4%. The proximity of the model to the ground also affects the longitudinal stability of the model. The moment coefficient curves against angle of attack has negative slope for both in and out of ground effect indicating favorable longitudinal stability. However, it was found that the aerodynamic center move further aft toward the trailing edge when the model move closer to the ground.

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