• International Journal of Naval Architecture and Ocean Engineering
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• v.10 no.4
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• pp.477-490
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• 2018

Effects of inflow Reynolds number (Re), turbulence intensity (I) and pressure gradient on the transition flow over a blade section were studied using the ${\gamma}-Re{\theta}$ transition model (STAR-CCM+). Results show that the $Re_T$ (transition Re) at the transition location ($P_T$) varies strongly with Re, I and the magnitude of pressure gradient. The $Re_T$ increases significantly with the increase of the magnitude of favorable pressure gradient. It demonstrates that the $Re_T$ on different blade sections of a rotating propeller are different. More importantly, when there is strong adverse pressure gradient, the $P_T$ is always close to the minimum pressure point. Based on these conclusions, the $P_T$ on model propeller blade surface can be estimated. Numerical investigations of pressure distribution and transition flow on a propeller blade section prove these findings. Last, a simple method was proposed to estimate the $P_T$ only based on the propeller geometry and the advance coefficient.

• International Journal of Aeronautical and Space Sciences
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• v.15 no.4
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• pp.345-355
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• 2014

This paper focuses on aerodynamic and inertial modeling of the propeller for its applications in flight dynamics analyses of a propeller-driven airplane. Unsteady aerodynamic and inertial loads generated by the propeller are formulated using the blade element method, where the local velocity and acceleration vectors for each blade element are obtained from exact kinematic relations for general maneuvering conditions. Vortex theory is applied to obtain the flow velocities induced by the propeller wake, which are used in the computation of the aerodynamic forces and moments generated by the propeller and other aerodynamic surfaces. The vortex lattice method is adopted to obtain the induced velocity over the wing and empennage components and the related influence coefficients are computed, taking into account the propeller induced velocities by tracing the wake trajectory trailing from each of the propeller blades. Aerodynamic forces and moments of the fuselage and other aerodynamic surfaces are computed by using the wind tunnel database and applying strip theory to incorporate viscous flow effects. The propeller models proposed in this paper are applied to predict isolated propeller performances under steady flight conditions. Trimmed level forward and turn flights are analyzed to investigate the effects of the propeller on the flight characteristics of a propeller-driven light-sports airplane. Flight test results for a series of maneuvering flights using a scaled model are employed to run the flight dynamic analysis program for the proposed propeller models. The simulations are compared with the flight test results to validate the usefulness of the approach. The resultant good correlations between the two data sets shows the propeller models proposed in this paper can predict flight characteristics with good accuracy.

• International Journal of Fluid Machinery and Systems
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• v.6 no.3
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• pp.144-151
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• 2013

In this paper, the design method of a low-head propeller-type hydro turbine is studied for various numbers of blades on an axial propeller. We also investigate the relationship between geometrical parameters and internal performance parameters, such as angular velocities (100, 200, 300, 400 rpm) and 2.5~4m low heads through a three-dimensional numerical method with the SST turbulent model. The numerical results showed that the blade number had a more dominant influence than the change in heads and rotational speed on the flow characteristics of the turbine. The distributions of pressure and velocity in the streamwise direction of the propeller turbine were graphically depicted. Especially, the relationship among dimensionless parameters like specific speed ($N_s$), flow coefficient (${\phi}$) and power coefficient (P) were investigated.

• Journal of the Korean Society of Propulsion Engineers
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• v.9 no.1
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• pp.46-52
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• 2005

A propeller as a propulsion system has been redesigned to improve performance of a target drone. The vortex theory has been applied for the propeller design method. Design variables have been the chord length along the direction of blade radius, the change of blade radius, and the geometric angle of the blade. The existing propeller has been redesigned and modified considering engine RPM change to get the improved thrust at both low and high speeds.

• Journal of the Society of Naval Architects of Korea
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• v.28 no.2
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• pp.40-51
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• 1991

A Propeller design method using the newly developed blade section(KH18), which behaves better cavitation characteristics, is presented. Experimental results for two-dimensional foil sections show that the lift-drag curve and the cavitation-free bucket diagram of the new blade section are wider comparing to those of the existion NACA sections. This characteristic of the new section is particularly important for marine propeller applications since angle of attack variation of the propeller blade operating behind a non-uniform ship's wake is relatively large. A lifting surface theory is used for the design of a propeller with the developed section for a 2700 TEU container ship. Since the most suitable chordwise loading shape is not known a priori, chordwise loading shape is chosen as a design parameter. Five propellers with different chordwise loading shapes and different foil sections are designed and tested in the towing tank and cavitation tunnel at KRISO. It is observed by a series of extensive model tsets that the propeller(KP197) having the chordwise loading shape, which has less leading edge loading at the inner radii and more leading edge loading at the outer radii of 0.7 radius, has higher propulsive efficiency and better cavitation characteristics. The KP197 propeller shows 1% higher efficiency, 30% cavitation volume reduction and 9% reduction of fluctuating pressure level comparing to the propeller with an NACA section. More appreciable efficiency gain for the new blade section propeller would be expected by reduction of expanded blade area considering the better cavitation characteristics of the new blade section.

• Journal of the Society of Naval Architects of Korea
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• v.48 no.6
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• pp.501-508
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• 2011

In order to control the tip vortex cavitation occurring around the tip of a rotating propeller blade, researches on the propeller cavitation and blade tip vortex flows have been increased. In this paper, the propeller tip vortex flow for a blunt and sharp tips was studied using an unsteady Reynolds-averaged Navier-Stokes equations solver based on a cell-centered finite volume method. In numerical open water test, torques, thrusts, pressure distributions and vortex flows were compared for various rotating speeds. To consider a hull wake, the nominal wake was specified in inlet boundary condition. Pressure distributions and vortex flows with the hull wake were investigated for various propeller rotating angles. From the results, it was confirmed that the blunt tip propeller delayed the tip vortex flow.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.12
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• pp.1716-1723
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• 2003

A stereoscopic PIV(Particle Image Velocimetry) technique was employed to measure the 3 dimensional flow structure of turbulent wake behind a marine propeller with 5 blades. The out-of-plane velocity component was determined using two CCD cameras with the angular displacement configuration. Four hundred instantaneous velocity fields were measured for each of four different blade phases and ensemble averaged to investigate the spatial evolution of the propeller wake in the near-wake region from the trailing edge to one propeller diameter(D) downstream. The phase-averaged velocity fields show the potential wake and the viscous wake developed along the blade surfaces. Tip vortices were generated periodically and the slipstream contraction occurs in the near-wake region. The out-of-plane velocity component and strain rate have large values at the locations of tip and trailing vortices. As the flow goes downstream, the turbulence intensity, the strength of tip vortices and the magnitude of out-of-plane velocity component at trailing vortices are decreased due to viscous dissipation, turbulence diffusion and blade-to-blade interaction.

• Journal of the Society of Naval Architects of Korea
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• v.35 no.1
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• pp.80-87
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• 1998

This paper deals with the evaluation of structural safety to fatigue strength of marine propeller blades having high skew angle and operating in irregular wake field. The determination of the optimum skew angle of a propeller blade is one of the important task at the initial design stage especially in the case of high speed vessel such as container ships. A computer program system has been developed to evaluate the structural safety to fatigue strength and has been applied to several propeller blades with varying skew angle within a wide range. In the parametric study the pressure acting on the blade surface is calculated using the non-lineal lifting surface theory and the structural analysis is performed using MSC/NASTRAN. The relationship between skew angle and structural safety to fatigue strength is investigated and this paper ends with describing the optimum skew angle of a propeller blade.

• Selected Papers of The Society of Naval Architects of Korea
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• v.1 no.1
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• pp.76-90
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• 1993

A new propeller series is developed using the newly developed blade section (KH 18 section) which has better cavitation characteristics and higher lift-drag ratio at wade angle-of-attack range than a conventional section. The radial patch distribution of the new series propellers is variable stance they were designed adaptively to a typical wake distribution. Basic geometric particulars of the series propellers. such as chord length, thickness, skew and rake distributions, are determined on the basis of recent full scale propeller geometric data. The series is developed for propellers having 4 blades, and blade area ratios of 0.3, 0.45, 0.6 and 0.75. Mean pitch ratios are varied as 0.5, 0.6, 0.7, 0.95 and 1.1 for each blade area ratio. The new propeller series consists of 20 propellers and is named as the KD(KRISO-DAEWOO)-propeller series. Propeller open-water tests are performed at the towing tank, and cavitation observation tests and fluctuating pressure tests are carried out at the cavitation tunnel of KRISO. $B_{p}-\delta$ curves, which can be used to select the optimum propeller diameter at the preliminary design stage, are derived from a regression analysis of the propeller open-water test results. The KD-cavitation chart is derived from the cavitation observation test results by choosing the local maximum lift coefficient and the local cavitation number as parameters. The cavity extent predicted by the KD-cavitation chart would be more accurate compared to that by an existing cavitation charts, such as the Burrll's cavitation chart, since the former is derived from the cavitation observation test results in a typical ship's wake, while the lather is derived from the test results in a uniform flow.

• Ocean Systems Engineering
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• v.11 no.4
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• pp.373-392
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• 2021

The present paper purposes a numerical evaluation of the Thai Long-Tail Boat propeller (TLTBP) performance by without and with propeller boss cap fins (PBCF) in full-scale operating straight shaft condition in the first. Next, those are applied to inclined shaft conditions. The actual TLTBP has defined an inclined shaft propeller including the high rotational speed, therefore vortex from the propeller boss and boss cap (hub vortex) have been generated very much. The PBCF designs are considered to weaken of vortex behind the propeller boss which makes the saving energy for the propulsion systems. The blade sections of PBCF developed from the original TLTBP blade shape. The integrative for the TLTBP and the PBCF is analyzed to increase the performance using computational fluid dynamics (CFD). The computational results of propeller performance are thoroughly compared between without and with PBCF. Moreover, the effects of each PBCF component are computed to influence the TLTBP performance. The fluid flows around the propeller blades, propeller boss, boss cap, and vortex have been investigated in terms of pressure distribution and wake-fields to verify the increasing efficiency of propulsion systems.