The Experts below are selected from a list of 162 Experts worldwide ranked by ideXlab platform
Koichi Koyama - One of the best experts on this subject based on the ideXlab platform.
-
Relation between the lifting Surface Theory and the lifting line Theory in the design of an optimum screw propeller
Journal of Marine Science and Technology, 2013Co-Authors: Koichi KoyamaAbstract:A Theory on an optimum screw propeller is described. The optimum means optimum efficiency of a propeller, that is, maximizing thrust horse power for a given shaft horse power. The Theory is based on the propeller lifting Surface Theory. Circulation density (lift density) of the blade is determined by the lifting Surface Theory on a specified condition in general. However, it is shown that, in the case of optimum condition, the circulation density is not determined by the lifting Surface Theory, although the circulation distribution which is the chordwise integral of the circulation density is determined. The reason is that the governing equation of the optimization by the lifting Surface Theory is reduced to that by the lifting line Theory. This theoretical deduction is the main part of this paper. The importance of the lifting line Theory in the design of the optimum propeller is made clear. Numerical calculations support the conclusion from the deduction. This is shown in the case of freely running propellers and in the case of wake adapted propellers.
Masanobu Namba - One of the best experts on this subject based on the ideXlab platform.
-
Unsteady Lifting Surface Theory for Supersonic Through-Flow Fan
JSME International Journal Series B, 1994Co-Authors: Masanobu Namba, Toshiya HanadaAbstract:The purpose of the present study is to predict analytically the unsteady loading on vibrating blades of a supersonic through-flow fan and investigate the aerodynamic instability. It is assumed that each blade operates with zero steady loading, and vibrates with small displacement amplitude, and a linearized unsteady lifting Surface Theory for a supersonic through-flow fan on the basis of the finite radial eigenfunction series approximation is developed. Numerical results of the unsteady loadings and unsteady aerodynamic works are presented. The bending vibration with zero mean loading is always stable, and the torsional instability heavily depends upon relative locations of the leading edge Mach wave reflection point and the torsion axis.
-
unsteady lifting Surface Theory based on double linearization concept for supersonic through flow fan
Transactions of the Japan Society of Mechanical Engineers. B, 1994Co-Authors: Toshiya Hanada, Masanobu NambaAbstract:A full three-dimensional lifting Surface Theory based on the double linearization concept is developed for a rotating annular cascade model operating at axial supersonic velocity. It is assumed that each blade vibrates with infinitesimal displacement amplitude under small mean loading. Vibration modes normal and parallel to the blade chord are considered. Numerical results are presented to investigate the mean loading effects on the aerodynamic instability of the blade motion. It is found that the bending motion can be unstable due to the presence of mean loading. Some numerical results compared with strip Theory predictions demonstrate significant three-dimensional effects on the unsteady aerodynamic force.
-
Lifting Surface Theory for Steady Aerodynamic Analysis of Ducted Counter Rotation Propfan
Volume 1: Turbomachinery, 1992Co-Authors: Hidekazu Kodama, Masanobu NambaAbstract:A lifting Surface Theory is developed to predict the steady performance for ducted counter rotation propfan with blade sweep. In solving the integral equation, the chordwise lifting pressures on the blade Surfaces of front and rear rotors are expanded into a finite series at each radial collocation point, and the coefficients of the series are determined so that the blade Surface flow tangency conditions for both rotors are satisfied at the corresponding number of control points. Calculations are carried out for the propfans with subsonic relative flows, and the effect of the number of blades on the total pressure rise is studied using a probable blade model. The interference effect between the rotors and the effect of blade sweep on the steady performance are also demonstrated.Copyright © 1992 by ASME
-
unsteady lifting Surface Theory for supersonic through flow fan
Transactions of the Japan Society of Mechanical Engineers. C, 1992Co-Authors: Masanobu Namba, Toshiya HanadaAbstract:The purpose of this work is to predict analytically the unsteady loading on vibrating blades of a supersonic through-flow fan and investigate the aerodynamic instability. In order to deal with this problem, a linearized unsteady lifting Surface Theory on the basis of the finite radial eigenfunction series approxmation is developed. It is assumed that each blade operates with zero mean loading, and vibrates with a small displacement amplitude. Numerical results for pure bending, pure torsional and combined bending and torsional vibrations are presented to demonstrate influences of interblade phase angle, location of torsion axis, axial Mach number and reduced frequency on the flutter boundary.
-
Unsteady lifting Surface Theory for a rotating transonic cascade of swept blades
Volume 5: Manufacturing Materials and Metallurgy; Ceramics; Structures and Dynamics; Controls Diagnostics and Instrumentation; Education; IGTI Scholar, 1991Co-Authors: Hidekazu Kodama, Masanobu NambaAbstract:A lifting Surface Theory is developed to predict the unsteady three-dimensional aerodynamic characteristics for a rotating transonic annular cascade of swept blades. An improved method is used to solve the integral equation for the unsteady blade loading. Numerical examples are presented to demonstrate effects of the sweep on the blade flutter and on the acoustic field generated by interaction of rotating blades with a convected sinusoidal gust. It is found that, in the case of transonic rotors, the magnitude of total aerodynamic work due to the blade vibration is reduced at large sweep angles, however blade sweep is not beneficial for noise reduction.Copyright © 1991 by ASME
Ray M. Chi - One of the best experts on this subject based on the ideXlab platform.
-
An unsteady lifting Surface Theory for ducted fan blades
Journal of Turbomachinery, 1993Co-Authors: Ray M. ChiAbstract:A frequency domain lifting Surface Theory is developed to predict the unsteady aerodynamic pressure loads on oscillating blades of a ducted subsonic fan. The steady baseline flow as observed in the rotating frame of reference is the helical flow dictated by the forward flight speed and the rotational speed of the fan. The unsteady perturbation flow, which is assumed to be potential, is determined by solving an integral equation that relates the unknown jump in perturbation velocity potential across the lifting Surface to the upwash velocity distribution prescribed by the vibratory motion of the blade. Examples of unsteady pressure distributions are given to illustrate the differences between the three-dimensional lifting Surface analysis and the classical two-dimensional strip analysis. The effects of blade axial bending, bowing (i.e., circumferential bending), and sweeping on the unsteady pressure load are also discussed.
-
An Unsteady Lifting Surface Theory for Ducted Fan Blades
Volume 5: Manufacturing Materials and Metallurgy; Ceramics; Structures and Dynamics; Controls Diagnostics and Instrumentation; Education; IGTI Scholar, 1991Co-Authors: Ray M. ChiAbstract:A frequency domain lifting Surface Theory is developed to predict the unsteady aerodynamic pressure loads on oscillating blades of a ducted subsonic fan. The steady baseline flow as observed in the rotating frame of reference is the helical flow dictated by the forward flight speed and the rotational speed of the fan. The unsteady perturbation flow, which is assumed to be potential, is determined by solving an integral equation that relates the unknown jump in perturbation velocity potential across the lifting Surface to the upwash velocity distribution prescribed by the vibratory motion of the blade. Examples of unsteady pressure distributions are given to illustrate the differences between the three dimensional lifting Surface analysis and the classical two dimensional strip analysis. The effects of blade axial bending, bowing (i.e., circumferential bending) and sweeping on the unsteady pressure load are also discussed.Copyright © 1991 by ASME
Cristinel Mardare - One of the best experts on this subject based on the ideXlab platform.
-
A New Approach to the Fundamental Theorem of Surface Theory
Archive for Rational Mechanics and Analysis, 2008Co-Authors: Philippe G. Ciarlet, Liliana Gratie, Cristinel MardareAbstract:The fundamental theorem of Surface Theory classically asserts that, if a field of positive-definite symmetric matrices ( a _ αβ ) of order two and a field of symmetric matrices ( b _ αβ ) of order two together satisfy the Gauss and Codazzi-Mainardi equations in a simply connected open subset ω of $${\mathbb{R}}^{2}$$ , then there exists an immersion $${\bf \theta}:\omega \to {\mathbb{R}}^{3}$$ such that these fields are the first and second fundamental forms of the Surface $${\bf \theta}(\omega)$$ , and this Surface is unique up to proper isometries in $${\mathbb{R}}^3$$ . The main purpose of this paper is to identify new compatibility conditions, expressed again in terms of the functions a _ αβ and b _ αβ , that likewise lead to a similar existence and uniqueness theorem. These conditions take the form of the matrix equation $$\partial{\bf A}_2-\partial_2{\bf A}_1+{\bf A}_1{\bf A}_2-{\bf A}_2{\bf A}_1={\bf 0}\,{\rm in}\,\omega,$$ where A _1 and A _2 are antisymmetric matrix fields of order three that are functions of the fields ( a _ αβ ) and ( b _ αβ ), the field ( a _ αβ ) appearing in particular through the square root U of the matrix field $${\bf C} = \left(\begin{array}{lll} a_{11} & a_{12} & 0\\ a_{21} & a_{22} & 0\\ 0 & 0 & 1\end{array}\right).$$ The main novelty in the proof of existence then lies in an explicit use of the rotation field R that appears in the polar factorization $${\bf \nabla}{\bf \Theta}={\bf RU}$$ of the restriction to the unknown Surface of the gradient of the canonical three-dimensional extension $${\bf \Theta}$$ of the unknown immersion $${\bf \theta}$$ . In this sense, the present approach is more “geometrical” than the classical one. As in the recent extension of the fundamental theorem of Surface Theory set out by S. M ardare [20–22], the unknown immersion $${\bf \theta}: \omega \to {\mathbb{R}}^3$$ is found in the present approach to exist in function spaces “with little regularity”, such as $$W^{2,p}_{\rm loc}(\omega;{\mathbb{R}}^3)$$ , p > 2. This work also constitutes a first step towards the mathematical justification of models for nonlinearly elastic shells where rotation fields are introduced as bona fide unknowns.
-
A new approach to the fundamental theorem of Surface Theory
Archive for Rational Mechanics and Analysis, 2008Co-Authors: Philippe G. Ciarlet, Liliana Gratie, Cristinel MardareAbstract:The fundamental theorem of Surface Theory classically asserts that, if a field of positive-definite symmetric matrices (a_{αβ}) of order two and a field of symmetric matrices (b_{αβ}) of order two together satisfy the Gauss and Codazzi-Mainardi equations in a simply connected open subset ω of R^2, then there exists an immersion θ : ω → R^3 such that these fields are the first and second fundamental forms of the Surface θ(ω), and this Surface is unique up to proper isometries in R^3. The main purpose of this paper is to identify new compatibility conditions, expressed again in terms of the functions a_{αβ} and b_{αβ}, that likewise lead to a similar existence and uniqueness theorem. These conditions take the form of the matrix equation ∂_1A_2−∂_2A_1+A_1A_2−A_2A_1=0 inω, where A_1 and A_2 are antisymmetric matrix fields of order three that are functions of the fields (a_{αβ}) and (b_{αβ}), the field (a_{αβ}) appearing in particular through the square root U of the matrix field a_{11} a_{12} 0 C = a_{21} a_{22} 0 0 0 1 The main novelty in the proof of existence then lies in an explicit use of the rotation field R that appears in the polar factorization ∇Θ = RU of the restriction to the unknown Surface of the gradient of the canonical three-dimensional extension Θ of the unknown immersion θ. In this sense, the present approach is more “geometrical” than the classical one. As in the recent extension of the fundamental theorem of Surface Theory set out by S. Mardare [2007], the unknown immersion θ : ω → R^3 is found in the present approach in function spaces “with little regularity”, such as W^{2,p}_loc(ω;R^3), p > 2. This work also constitutes a first step towards the mathematical justification of models for nonlinearly elastic shells where rotation fields are introduced as bona fide unknowns.
-
New compatibility conditions for the fundamental theorem of Surface Theory
Comptes Rendus Mathématique, 2007Co-Authors: Philippe G. Ciarlet, Liliana Gratie, Cristinel MardareAbstract:The fundamental theorem of Surface Theory classically asserts that, if a field of positive-definite symmetric matrices (a_{αβ}) of order two and a field of symmetric matrices (b_{αβ}) of order two together satisfy the Gauss and Codazzi–Mainardi equations in a connected and simply-connected open subset ω of R^2, then there exists an immersion θ : ω → R^3 such that these fields are the first and second fundamental forms of the Surface θ(ω) and this Surface is unique up to proper isometries in R^3. In this Note, we identify new compatibility conditions, expressed again in terms of the functions a_{αβ} and b_{αβ}, that likewise lead to a similar existence and uniqueness theorem. These conditions take the form ∂_1A_2−∂_2A_1+A_1A_2−A_2A_1=0 in ω, where A_1 and A_2 are antisymmetric matrix fields of order three that are functions of the fields (a_{αβ}) and (b_{αβ}), the field (a_{αβ}) appearing in particular through its square root. The unknown immersion θ : ω → R^3 is found in the present approach in function spaces ‘with little regularity’, viz., W^{2,p}_loc(ω;R^3), p > 2.
Samira Pourhedayat - One of the best experts on this subject based on the ideXlab platform.
-
Analytical/experimental sensitivity study of key design and operational parameters of perforated Maisotsenko cooler based on novel wet-Surface Theory
Applied Energy, 2020Co-Authors: Hamed Sadighi Dizaji, Lei Chen, Samira PourhedayatAbstract:Abstract Only one analytical model was previously proposed for multi-stage M-cycle cooler which is based on Sprayed-Water Theory in which the temperature of the wet plate was assumed constant, equal to water inlet temperature, (as the water flow rate was assumed so high). Said preliminary model was only able to predict outlet characteristics of the cooler (not parameters distribution along the cooler). This paper presents a new model for multi-stage M-cycle cooler based on the novel Wet-Surface Theory in which the temperature of the wet-plate varies along the cooler (real working condition) and the model is able to generate the temperature/humidity distribution in addition to the outlet characteristics. The concept of the novel Wet-Surface Theory and its potentials are discussed in the paper. Maximum theoretic cooling capacity of a given M-cycle cooler is obtained when it works based on Wet-Surface Theory. The model is experimentally validated with a unique test-rig and then the impacts of key operation and design parameters of multi-stage M-cycle cooler (i.e. inlet temperature, humidity ratio, mass flow rate, mass flow ratio, channel gap, channel length, channel height and the location of perforation) on its cooling characteristics (including outlet temperatures, outlet humidity ratio, wet-bulb effectiveness and dew-point effectiveness) are studied by the validated model.
