Specification of Acceptable Blade Porosity for Cavitation Performance of Marine Propellers

2003 ◽  
Author(s):  
David R. Stinebring ◽  
William A. Straka ◽  
W. R. Hall
Keyword(s):  
Blade Surface ◽  
Propeller Blade ◽  
Cavitation Inception ◽  
Local Boundary ◽  
Marine Propellers ◽  
Surface Pressure Distribution ◽  
Cavitation Performance ◽  
Penn State ◽  
Propeller Blades ◽  
Made In

The issues of cavitation inception for porosity for cast propeller blades are addressed. Desinent cavitation measurements were made in the ARL Penn State 48-inch diameter water tunnel for a series of holes machined into inserts mounted in the tunnel test section. The data were compared to previous measurements with slots and isolated roughnesses. A design exercise is presented for a generic propeller blade to specify “acceptable” blade porosity for a given cavitation inception goal. The application to the blade accounts for the spanwise velocity distribution, local blade surface pressure distribution, local boundary layer thickness, and porosity size. The final result is a mapping of ranges in acceptable porosity for locations on the blade.

scholarly journals Influence of wall roughness on cavitation performance of centrifugal pump

2021 ◽  
Vol 43 (6) ◽  
Author(s):  
Weihui Xu ◽  
Xiaoke He ◽  
Xiao Hou ◽  
Zhihao Huang ◽  
Weishu Wang
Keyword(s):  
Flow Field ◽  
Centrifugal Pump ◽  
Internal Flow ◽  
Wall Roughness ◽  
Blade Surface ◽  
Centrifugal Pumps ◽  
Three Dimensional Model ◽  
Cavitation Inception ◽  
Cavitation Performance ◽  
Critical Cavitation

AbstractCavitation is a phenomenon that occurs easily during rotation of fluid machinery and can decrease the performance of a pump, thereby resulting in damage to flow passage components. To study the influence of wall roughness on the cavitation performance of a centrifugal pump, a three-dimensional model of internal flow field of a centrifugal pump was constructed and a numerical simulation of cavitation in the flow field was conducted with ANSYS CFX software based on the Reynolds normalization group k-epsilon turbulence model and Zwart cavitation model. The cavitation can be further divided into four stages: cavitation inception, cavitation development, critical cavitation, and fracture cavitation. Influencing laws of wall roughness of the blade surface on the cavitation performance of a centrifugal pump were analyzed. Research results demonstrate that in the design process of centrifugal pumps, decreasing the wall roughness appropriately during the cavitation development and critical cavitation is important to effectively improve the cavitation performance of pumps. Moreover, a number of nucleation sites on the blade surface increase with the increase in wall roughness, thereby expanding the low-pressure area of the blade. Research conclusions can provide theoretical references to improve cavitation performance and optimize the structural design of the pump.

A Method for Propeller Blade Optimization and Cavitation Inception Mitigation

2015 ◽  
Vol 31 (02) ◽  
pp. 88-98
Author(s):  
Brenden Epps ◽  
Oscar Víquez ◽  
Chryssostomos Chryssostomidis
Keyword(s):  
High Speed ◽  
Maximum Speed ◽  
Propeller Blade ◽  
Lower Efficiency ◽  
Design Point ◽  
Operational Conditions ◽  
Cavitation Inception ◽  
Cavitation Performance ◽  
Blade Shape ◽  
Present Design

Propeller blade design for fast ships is often driven by cavitation constraints. A tradeoff exists, in which larger chord lengths and section thicknesses typically improve cavitation performance but result in lower efficiency. Typically, chord lengths are optimized for the design condition (ship endurance speed) with some specified margin to prevent cavitation off-design (at maximum ship speed). Cavitation performance at the maximum speed is considered postfacto, and blade shape often needs to be modified for cavitation considerations in high-speed operation. This article presents an improved method for blade shape optimization. The present method simultaneously considers the cavitation performance at the endurance speed design point and a maximum speed off-design point, and blade chord lengths and thicknesses are set to prevent cavitation at both operational conditions. During the present design optimization routine, the on-design load distribution is optimized, and the off design performance is determined such that the chord lengths can be set to a minimum that still prevents cavitation at both the on- and off-design conditions. A case study is presented, considering the notional design of a propeller for the U.S. Navy DDG51 destroyer-class ship. Propellers designed using standard chord/thickness optimization procedures are compared with those designed using the present procedures. Cavitation performance is compared for the two design methods.

Flow Around the Revolving Propeller Blades in Low Reynolds Number Field

2007 ◽  
Author(s):  
Nobuyuki Arai ◽  
Hironori Yoshida ◽  
Katsumi Hiraoka
Keyword(s):  
Reynolds Number ◽  
Wind Tunnel ◽  
Number Field ◽  
Wind Tunnel Testing ◽  
Edge Region ◽  
Blade Surface ◽  
Propeller Blade ◽  
Trailing Edge ◽  
Propulsion Efficiency ◽  
Propeller Blades

By studying the flow around the revolving propeller blades, an improvement of the propulsion efficiency can be found. We made the propeller blade optimized to get good propulsion efficiency by the Adkins & Liebeck’s propeller theory in low Reynolds number field. We call this blade “Prop00”. In order to investigate the flow around the propeller blades, distributions of pressure on the surface of the revolving propeller blade in some pitch angles were measured by wind tunnel testing. For Prop00, it was observed that the contour lines of Cp are dense near the trailing edge of blade’s tip. And it is thought that the separation may exist around the tip of blade. In order to compare the flow characteristics and to get the hint of improvement of the shape of the propeller blades, three different shape types of propeller blades, rectangle, trapezoid, and inverted trapezoid, were made. We call these blades “Prop01”, “Prop02”, and “Prop03”, respectively. According to the pressure distribution, it’s necessary to improve the shape of the propeller which suppresses the effect by a separation to improve the propulsion efficiency more. We took some photographs of tufts on the revolving blades with stroboscope to investigate vectors of the flow on the blade surface. These photographs are taken under identical conditions of the direct pressure measurement. It was observed that tufts tend to bent to the outer side direction by centrifugal force. However, differences on tufts bending were observed in the regions of the leading and the trailing edges at same radius. The tufts at the trailing edge region more bent to the tip of blade than that at leading edge region. Then, it is thought that separation and crossflow on the blade surface exist. We thought that the stability of the flow around the trailing edge is lost by the separation and the boundary layer transition. Furthermore, universal CFD software is used to study the improvement of the propeller performance. By using FLUENT 6 as universal CFD software, the result of CFD was compared with the result of wind tunnel testing.

scholarly journals Measuring diameter of water jets affecting propeller blade surface under cavitation wear

2021 ◽  
Vol 2021 (1) ◽  
pp. 54-64
Author(s):  
Yuriy Nickolayevich Tsvetkov ◽  
Yaroslav Olegovich Fiaktistov ◽  
Evgeniy Olegovich Gorbachenko
Keyword(s):  
Hydrodynamic Cavitation ◽  
Cold Hardening ◽  
Mean Deviation ◽  
Blade Surface ◽  
Propeller Blade ◽  
Water Jets ◽  
Proportional Relationship ◽  
Cavitation Wear ◽  
Propeller Blades ◽  
Ship Propeller

The article analyses the structure of cavitated areas of the ship propeller blades made from aluminum bronzes with different composition. The most informative zones of cavitation wear are the cold-hardening zone and the peripheral one that help estimate the mechanical parameters causing the cavities to collapse. The dents formed on the metal surface in the process of hydrodynamic cavitation wear have spherical parts on their bottoms, in which it is possible to inscribe a circle of a definite diameter. There were conducted the experiments on forcing the ball indentors into the surface of different metal alloys. The first run of the experiments includes forcing of a steel ball with a diameter of 1.588 mm into the surface of 33 alloys with different hardness under the loads of 1 470, 980 and 588 N. The impression diameters were measured using Brinell magnifying glass. There has been found the power dependence between deformation of dents on the metals tested under hydrodynamic cavitation and hardness of the materials, which is similar to the dependence of deformation after forcing the ball indentors into the alloys of different hardness. The second run of the experiments included modeling the cold-hardening zone of the cavitation wear area by repeated forcing the ball indentors with the diameters of 1.588, 2.5, 3.175 and 5.0 mm into the bronze BrAZhNMts9-4-4-1 plates with area of 100 × 50 × 20 mm. Forcing was made into the side 100 × 50 mm previously ground and polished. The equal strain rate in impressions of different diameters was observed during forcing. A direct proportional relationship was obtained between the arithmetic mean deviation of the surface profile and the indenter diameter. The arithmetical mean deviation of the assessed profile of the side plotted against the ball indentor yields a direct proportional relationship. Using the dependence for the case of cavitation attack on the propeller blades helps to infer that the diameter of water jets striking against the propeller blade surface with diameter of 3 700 mm makes about 10 mm. The obtained value allows to choose reasonably the experimental equipment and the parameters of testing the ship propeller materials for cavitation wear.

Determination of Underwater Plate Dynamics Using Laser Beams

1974 ◽  
Vol 96 (3) ◽  
pp. 722-728
Author(s):  
Rudolph E. Croteau ◽  
Herman E. Sheets
Keyword(s):  
Near Field ◽  
Surface Displacement ◽  
Coupled System ◽  
Green Laser ◽  
Testing Facility ◽  
Acoustic Testing ◽  
Propeller Blades ◽  
The Relationship ◽  
Made In

Underwater plate vibration and its associated noise are of interest for the analysis of ship structures, propeller blades, and other areas of underwater acoustics. In order to analyze the relationship between a plate vibrating underwater and the acoustic pressure in the near-field, optical interferometric holography, using a blue-green laser beam, was used to determine surface displacement for the vibrating plate, which was excited through a fluid-coupled system. Acoustic measurements of the same source were made in a water tower concurrently with the holography and later at a precision acoustic testing facility. This method permits prediction of underwater plate modal frequencies and shapes with high accuracy.

Design Optimization of Cryogenic Pump Inducer Considering Suction Performance and Cavitation Instability

2011 ◽  
Author(s):  
Hiroyoshi Watanabe ◽  
Hiroshi Tsukamoto
Keyword(s):  
Pressure Distribution ◽  
Design Optimization ◽  
Surface Pressure ◽  
Design Approach ◽  
Inverse Design ◽  
Blade Surface ◽  
Free Vortex ◽  
Surface Pressure Distribution ◽  
Cavitation Instability ◽  
Suction Performance

This paper presents the result of design optimization for three-bladed pump inducer using a three-dimensional (3-D) inverse design approach, Computational Fluid Dynamics (CFD) and DoE (Design of Experiments) taking suction performance and cavitation instability into consideration. The parameters to control streamwise blade loading distribution and spanwise work (free vortex or non-free vortex) for inducer were chosen as design optimization variables for the inverse design approach. Cavitating and non-cavitating performances for inducers designed using the design variables arranged in the DoE table were analyzed by steady CFD. Objective functions for non-cavitating operating conditions were the head and efficiency of inducers at a design flow (Qd), 80% Qd and 120% Qd. The volume of the inducer cavity region with a void ratio above 50% was selected as the objective function for inducer suction performance. In order to evaluate cavitation instability by steady CFD, the dispersion of the blade surface pressure distribution on each blade was selected as the evaluation parameter. This dispersion of the blade surface pressure distribution was caused by non-uniformity in the cavitation length that was developed on each inducer blade and increased when the cavitation number was reduced. The effective design parameters on suction performance and cavitation instability were confirmed by sensitivity analysis during the design optimization process. Inducers with specific characteristics (stable, unstable) designed using the effective parameters were evaluated through experiments.

Surface Pressure Distribution on a Blade of a 10 m Diameter HAWT (Field Measurements versus Wind Tunnel Measurements)

2005 ◽  
Vol 127 (2) ◽  
pp. 185-191 ◽  
Author(s):  
T. Maeda ◽  
E. Ismaili ◽  
H. Kawabuchi ◽  
Y. Kamada
Keyword(s):  
Wind Tunnel ◽  
Surface Pressure ◽  
Field Measurements ◽  
Reynolds Numbers ◽  
Blade Surface ◽  
Pressure Data ◽  
Surface Pressure Distribution ◽  
Pressure Distributions ◽  
Wind Tunnel Data ◽  
Local Angle

This paper exploits blade surface pressure data acquired by testing a three-bladed upwind turbine operating in the field. Data were collected for a rotor blade at spanwise 0.7R with the rotor disc at zero yaw. Then, for the same blade, surface pressure data were acquired by testing in a wind tunnel. Analyses compared aerodynamic forces and surface pressure distributions under field conditions against analogous baseline data acquired from the wind tunnel data. The results show that aerodynamic performance of the section 70%, for local angle of attack below static stall, is similar for free stream and wind tunnel conditions and resemblances those commonly observed on two-dimensional aerofoils near stall. For post-stall flow, it is presumed that the exhibited differences are attributes of the differences on the Reynolds numbers at which the experiments were conducted.

scholarly journals Roughness of propeller blade surface and its implications for propulsion performance

2019 ◽  
Vol 4 (390) ◽  
pp. 11-26
Author(s):  
A. Pustoshny ◽  
◽  
A. Sverchkov ◽  
S. Shevtsov ◽  
◽  
...  
Keyword(s):  
Blade Surface ◽  
Propeller Blade ◽  
Propulsion Performance

Numerical Study on Multiple-Blade-Rate Unsteady Propeller Forces for Underwater Vehicles

2021 ◽  
pp. 1-20
Author(s):  
Kenshiro Takahashi ◽  
Jun Arai ◽  
Takayuki Mori
Keyword(s):  
Numerical Study ◽  
Underwater Vehicles ◽  
Marine Propellers ◽  
Defense Systems ◽  
Detection Technology ◽  
Acoustic Signature ◽  
Océanographic Survey ◽  
Propeller Blades ◽  
Marine Vessels ◽  
Blade Loads

The unsteady propeller forces of an underwater vehicle were numerically simulated using computational fluid dynamics to investigate the effects of the axial location of the stern planes. A benchmark study was undertaken using a three-bladed propeller; experimental results of the nominal inflow wake profile were analyzed and the unsteady propeller forces were measured. The numerical method was applied to predict the unsteady propeller forces in the SUBOFF model’s wake by varying the axial locations of the stern planes. Several remarks were made on the primary harmonics of the hull’s wakes and blade-rate propeller forces. Introduction The hydroacoustic noise, which matches multiples of the number of propeller blades and its rotational speed, known as “blade-rate (BR) noise,” has been increasingly used to manage hydroacoustics for naval vessels. BR noise can be caused by alternating blade loads owing to fluctuations in the angle of attack of the blades because marine propellers are operated in the nonuniform wake of ships’ hulls. The unsteady blade load produces unsteady propeller forces that are transmitted via the propeller shaft and bearing, thus producing undesirable vibration and noise. Although the resultant BR noise is a common issue for marine vessels, in particular, submarines and other underwater vehicles deployed for undersea defense systems and oceanographic survey systems require strict specifications for the acoustic signature. Therefore, the unsteady propeller forces must be improved for reduced detectability, because the vehicles should be able to operate without being discovered while sonar detection technology continues to improve.

scholarly journals On Structural Optimization of the Propeller Blade

2018 ◽  
Vol 7 (4.36) ◽  
pp. 1203
Author(s):  
Mikhail Aleshin ◽  
Aleksandr Smirnov ◽  
Margarita Murzina ◽  
Yuri Boldyrev
Keyword(s):  
Composite Material ◽  
Structural Optimization ◽  
Computational Time ◽  
Geometrical Parameters ◽  
Propeller Blade ◽  
Aerodynamic Loads ◽  
Change Mechanism ◽  
Blade Shape ◽  
Optimization Parameters ◽  
Propeller Blades

The results of the structural optimization of propeller blades are presented taking into account its composite structure and pitch change mechanism of the propeller and using FSI (Fluid-Structure Interaction) approaches.  The optimality criterion of the problem is the propeller thrust with optimization parameters being the characteristics of the internal structure of the propeller blade made from a composite. Together with the optimization of the blade shape, the problem is considered which concerns the reduction of the deformations caused by loads occurring during the operation of the propeller, since significant deformations of the blades lead to decreased thrust.Thus, the following optimization problem can be formulated: to find the optimal configuration of the composite material and its micro-geometrical parameters along the height of the blade to minimize deformations and increase the thrust of the propeller.  At the same time, the optimization parameters are limited by the weight of the propeller and the strength characteristics.The technique presented in the paper allows us to obtain the reliable values of thrust and reduce the estimated computational time.  The influence of the structure of the composite material on the mechanical properties of the blades is shown; the values of deformation of the blades under the action of centrifugal and aerodynamic loads are given. 

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