Propeller Surface Research Articles

Wake-adapted design of fixed guide vane type energy saving device for marine propeller

A wake-adapted design method of downstream fixed guide vanes (FGV) for marine propeller is proposed based on propeller vortex theory (PVT) and surface panel method (SPM). The FGV is designed to recover the slipstream rotational energy of propeller into an additional thrust. The hydrodynamic interaction between the propeller and the FGV is the key point in the combined propulsor design and is considered through induced velocities calculated by SPM. As the guide vanes are fixed and work in nonuniform wake field, different blades have significantly different inflow velocities. Therefore, the blades of FGV ought to be designed independently. The radial circulation distributions of the combined propulsor as well as the tangential induced velocities in the slipstream are calculated to validate the energy saving principle of FGV. The results of design case study indicate that the FGV after propeller can recover the slipstream rotational energy of propeller effectively.

Compared with PI, Fuzzy-PI and PSO-PI Controllers of Robotic Grinding Force Servo System

By grinding process, when an industrial robot is used to finish a curved surface, both feed movement and contact force must controlled at the similar time in order that the grinding tool would machine the work-piece at the right position in right posture with required force. A passive wrist system is advanced, in this paper, to conform the shape of the machining propeller by altering its posture along with the surface. The proportional-integral (PI) controller, due to its simplicity, robustness, and affordable price, is extremely often used in practical applications, but it is effective for linear systems, as well as, the challenging task is to find its optimal gains. If the processes involved higher order and time delay systems, many intelligent controllers were appeared. In this paper, to cope with nonlinearities, improve the controller parameters and at the same time modeling uncertainties of grinding marine propeller surface, a PI torque controller is proposed such that its optimal gains are derived via a modern systems based on fuzzy logic theory and particle swarm optimization algorithm which are used to solve various engineering problems. Grinding force is controlled under Fuzzy-PI controller which is being assembled and compared with a PSO-PI controller to obtain which controller that provides grinding with higher quality. The compared controllers have been optimized together with the parameters of the Two-Phase Hybrid Stepping Motor. The suggested fuzzy rule function and PSO algorithm improve the response of the controlled system and searches a high-quality solution impressively. Simulation and comparison results are presented and that the proposed control systems are coping well with nonlinearities and uncertainties while find PI control parameter set effectively, the PSO-PI controller has a better control performance with improved step response for robotic grinding force servo system. These control methods was simulated using MATLAB/SIMULINK.

Compared with PI, Fuzzy-PI and PSO-PI Controllers of Robotic Grinding Force Servo System

<p>By grinding process, when an industrial robot is used to finish a curved surface, both feed movement and contact force must controlled at the similar time in order that the grinding tool would machine the work-piece at the right position in right posture with required force. A passive wrist system is advanced, in this paper, to conform the shape of the machining propeller by altering its posture along with the surface. The proportional-integral (PI) controller, due to its simplicity, robustness, and affordable price, is extremely often used in practical applications, but it is effective for linear systems, as well as, the challenging task is to find its optimal gains. If the processes involved higher order and time delay systems, many intelligent controllers were appeared. In this paper, to cope with nonlinearities, improve the controller parameters and at the same time modeling uncertainties of grinding marine propeller surface, a PI torque controller is proposed such that its optimal gains are derived via a modern systems based on fuzzy logic theory and particle swarm optimization algorithm which are used to solve various engineering problems. Grinding force is controlled under Fuzzy-PI controller which is being assembled and compared with a PSO-PI controller to obtain which controller that provides grinding with higher quality. The compared controllers have been optimized together with the parameters of the Two-Phase Hybrid Stepping Motor. The suggested fuzzy rule function and PSO algorithm improve the response of the controlled system and searches a high-quality solution impressively. Simulation and comparison results are presented and that the proposed control systems are coping well with nonlinearities and uncertainties while find PI control parameter set effectively, the PSO-PI controller has a better control performance with improved step response for robotic grinding force servo system. These control methods was simulated using MATLAB/SIMULINK.</p>

PSO_PI Controller of Robotic Grinding Force Servo System

When an industrial robot is used to grind a curved surface ,as marine propeller surface, contact force and feed movement must controlled together at the similar time in order that the grinding tool would machine the work-piece, with required force, at the right position in right posture. A passive wrist system is advanced, in this paper, to conform the shape of the machining propeller by altering its posture along with the surface. Grinding force is controlled under a simple new PSO-PI controller at a steady value in the normal direction of the mentioned machining point by multi-point machining, while the grinding tool moving along the curved surface of the propeller. It means that the model of the passive wrist system and the surroundings could be used in force controlling when robots grind marine propeller surface by a grinding tool with multi-point machining. PSO_PI controller policy is being assembled and compared with a PI controller to obtain a controller that provides grinding with higher quality. The compared controllers have been optimized together with the parameters of the Two-Phase Hybrid Stepping Motor. The particle swarm optimization (PSO) method was selected from several methods to optimize of Proportional-Integral controller parameters in order to give better performance with improved step response for robotic grinding force servo system and overshoot are reduced. This control method was simulated using MATLAB/SIMULINK.

PSO_PI Controller of Robotic Grinding Force Servo System

When an industrial robot is used to grind a curved surface ,as marine propeller surface, contact force and feed movement must controlled together at the similar time in order that the grinding tool would machine the work-piece, with required force, at the right position in right posture. A passive wrist system is advanced, in this paper, to conform the shape of the machining propeller by altering its posture along with the surface. Grinding force is controlled under a simple new PSO-PI controller at a steady value in the normal direction of the mentioned machining point by multi-point machining, while the grinding tool moving along the curved surface of the propeller. It means that the model of the passive wrist system and the surroundings could be used in force controlling when robots grind marine propeller surface by a grinding tool with multi-point machining. PSO_PI controller policy is being assembled and compared with a PI controller to obtain a controller that provides grinding with higher quality. The compared controllers have been optimized together with the parameters of the Two-Phase Hybrid Stepping Motor. The particle swarm optimization (PSO) method was selected from several methods to optimize of Proportional-Integral controller parameters in order to give better performance with improved step response for robotic grinding force servo system and overshoot are reduced. This control method was simulated using MATLAB/SIMULINK.

The crystal structure of the thiocyanate-forming protein from Thlaspi arvense, a kelch protein involved in glucosinolate breakdown.

Kelch repeat-containing proteins are involved in diverse cellular processes, but only a small subset of plant kelch proteins has been functionally characterized. Thiocyanate-forming protein (TFP) from field-penny cress, Thlaspi arvense (Brassicaceae), is a representative of specifier proteins, a group of kelch proteins involved in plant specialized metabolism. As components of the glucosinolate-myrosinase system of the Brassicaceae, specifier proteins determine the profile of bioactive products formed when plant tissue is disrupted and glucosinolates are hydrolyzed by myrosinases. Here, we describe the crystal structure of TaTFP at a resolution of 1.4 Å. TaTFP crystallized as homodimer. Each monomer forms a six-blade β-propeller with a wide "top" and a narrower "bottom" opening with distinct strand-connecting loops protruding far beyond the lower propeller surface. Molecular modeling and mutational analysis identified residues for glucosinolate aglucone and Fe(2+) cofactor binding within these loops. As the first experimentally determined structure of a plant kelch protein, the crystal structure of TaTFP not only enables more detailed mechanistic studies on glucosinolate breakdown product formation, but also provides a new basis for research on the diverse roles and mechanisms of other kelch proteins in plants.

後流渦の変形を考慮した二重反転プロペラの定常性能解析

To reduce fuel oil costs and emission of greenhouse gases of ships in operation, application of Contra-Rotating Propellers (CRP) will be one of the solutions, which have high propulsive efficiency. Although several estimation methods of predicting open water characteristics of CRP have been developed in the past, few methods treat accurately with trailing wake geometry, which influences much on estimate accuracy. CRP makes the flow around the propellers more complicated compared with conventional single propeller because aft and forward propeller of CRP interacts each other strongly. In order to improve estimate accuracy, more rigorous treatment of the trailing wake geometry is desirable. This paper presents a calculation method, taking deformation of trailing wake accurately into account. The method is based on a simplified surface panel method "SQCM" which satisfies the Kutta condition easily. The SQCM consists of Hess and Smith type source panels on the propeller surface and discrete vortices on the camber surface according to Lan's QCM (Quasi-Continuous vortex lattice Method). The wake vortex lines are arranged in accordance with the direction of the flow including induced velocity by both propellers. We show some calculated results and validate them by comparing experiments in this paper. It is found that thrust and torque of the aft propeller differ considerably depending on which the deformation of trailing wake is taken into account or not. The calculated results with deformed wake agrees very well with the experiment, while the calculated results without deformed wake always overestimate the thrust and torque of the aft propeller.

선박에서의 CO2배출량 저감 방안 연구

This Paper presented the reduction methods of <TEX>$CO_2$</TEX> emission from ships during voyage. In order to decrease <TEX>$CO_2$</TEX> emission during voyage the equation was established and conducted the study about the relationship between ship speed, the propulsive efficiency and its <TEX>$CO_2$</TEX> production. The results obtained from the examinations are as follows : 1. <TEX>$CO_2$</TEX> emission from sailing ships can be decreased by reducing specific fuel oil consumption of main diesel engine, coefficient of total resistance and ship speed and also by increasing propeller efficiency. 2. Diesel-electric propulsion system is more effective than diesel-mechanical system to decrease the level of <TEX>$CO_2$</TEX> emission during long voyage. 3. Good condition of ship's hull surface, rudder and propeller's surface can decrease the quantity of fuel oil and <TEX>$CO_2$</TEX> emission by reducing the resistance of ship that can rise the propeller efficiency 4. <TEX>$CO_2$</TEX> emitted from ships can be decreased in a global scale by giving attention to the synthetic transport efficiency.

The interplay between RPGR, PDEδ and Arl2/3 regulate the ciliary targeting of farnesylated cargo

Defects in primary cilia result in human diseases known as ciliopathies. The retinitis pigmentosa GTPase regulator (RPGR), mutated in the most severe form of the eye disease, is located at the transition zone of the ciliary organelle. The RPGR-interacting partner PDEδ is involved in trafficking of farnesylated ciliary cargo, but the significance of this interaction is unknown. The crystal structure of the propeller domain of RPGR shows the location of patient mutations and how they perturb the structure. The RPGR·PDEδ complex structure shows PDEδ on a highly conserved surface patch of RPGR. Biochemical experiments and structural considerations show that RPGR can bind with high affinity to cargo-loaded PDEδ and exposes the Arl2/Arl3-binding site on PDEδ. On the basis of these results, we propose a model where RPGR is acting as a scaffold protein recruiting cargo-loaded PDEδ and Arl3 to release lipidated cargo into cilia.

Numerical analysis of cavitating propeller and pressure fluctuation on ship stern using a simple surface panel method “SQCM”

This paper presents a calculation method for the pressure fluctuation induced by a cavitating propeller. This method consists of two steps: the first step is the calculation of propeller sheet cavitation, and the second step is the calculation of pressure fluctuation on the ship stern. It is for practicality that we divide the method into two steps but do not calculate these steps simultaneously. This method is based on a simple surface panel method “SQCM” which satisfies the Kutta condition easily. The SQCM consists of Hess and Smith type source panels on the propeller or cavity surface and discrete vortices on the camber surface according to Lan’s QCM (quasi-continuous vortex lattice method). In the first step, the cavity shape is solved by the boundary condition based on the free streamline theory. In order to get the accurate cavity shape near the tip of the propeller blade, the cross flow component is taken into consideration on the boundary condition. In the second step, we calculate the cavitating propeller and the hull surface flow simultaneously so as to calculate the pressure fluctuation including the interaction between the propeller and the hull. At that time, the cavity shape is changed at each time step using the calculated cavity shape gotten by the first step. Qualitative agreements are obtained between the calculated results and the experimental data regarding cavity shape, cavity volume and low order frequency components of the pressure fluctuation induced by the cavitating propeller.

Numerical Analysis of the Propeller Low Frequency Flow-Noise

In this paper，the numerical simulation of the propeller low frequency flow-noise was investigated，and the acoustic field of propeller DTMB P4119 at an advance ratio of 0.833 was studied. First，the temporal flow field was simulated with the Large-Eddy Simulation（LES）approach. Then，the K-FWH （Kirchhoff-Ffowcs Williams and Hawkings）equations were solved to obtain the low frequency flow-noise. By comparing the thrust coefficients and the torque coefficients calculated with experimental data，the correctness previously simulated temporal flow field could be verified. It could be observed from the simulated flow field that continuous vortex shedding does exist at the propeller surface. Also，the calculated acoustic field shows that（1）the magnitude of discrete noise dominates that of broadband noise；（2）the broadband noise is mainly induced by the vortex shedding phenomenon and is responsible for the circumference fluctuation of overall Sound Pressure Level（SPL）in the near region of the propeller；（3）the SPL at the same radius decreases gradually along the axial direction，and it experiences an initial increase，followed by a decreases along the radial direction.

Analysis of a propeller wake flow field using viscous fluid mechanics

The computational fluid dynamics (CFD) method is used to numerically simulate a propeller wake flow field in open water. A sub-domain hybrid mesh method was adopted in this paper. The computation domain was separated into two sub-domains, in which tetrahedral elements were used in the inner domain to match the complicated geometry of the propeller, while hexahedral elements were used in the outer domain. The mesh was locally refined on the propeller surface and near the wake flow field, and a size function was used to control the growth rate of the grid. Sections at different axial location were used to study the spatial evolution of the propeller wake in the region ranging from the disc to one propeller diameter (D) downstream. The numerical results show that the axial velocity fluctuates along the wake flow; radial velocity, which is closely related to vortices, attenuates strongly. The trailing vortices interact with the tip vortex at the blades’ trailing edge and then separate. The strength of the vortex shrinks rapidly, and the radius decreases 20% at one diameter downstream.

Numerical prediction of blade frequency noise of cavitating propeller

The blade frequency noise of a cavitating propeller in a uniform flow is analyzed in the time domain. The unsteady loading (of a dipole source) and the sheet cavity volume (of a monopole source) on the propeller surface are calculated by a potential-based surface panel method. Then the time-dependent pressure and the cavity volume data are used as the input for the Fowcs Williams-Hawkings formulation to predict the acoustics pressure. The integration of the noise source is performed over the true blade surface rather than the ideal blade surface without thickness. The noise characteristics of the cavitating propeller are discussed. With the sheet cavitation, the thickness (cavitation) noise is larger than the loading noise and is the dominant noise source. The noise directivity is not as clear as that of the noise under a non-cavitation condition. The cavitation noise is attenuated more slowly than the non-cavitation noise.

Crystal structures of the extracellular domain of LRP6 and its complex with DKK1

Low-density-lipoprotein (LDL) receptor-related proteins 5 and 6 (LRP5/6) are Wnt co-receptors essential for Wnt/β-catenin signaling. Dickkopf 1 (DKK1) inhibits Wnt signaling by interacting with the extracellular domains of LRP5/6 and is a drug target for multiple diseases. Here we present the crystal structures of a human LRP6-E3E4-DKK1 complex and the first and second halves of human LRP6's four propeller-epidermal growth factor (EGF) pairs (LRP6-E1E2 and LRP6-E3E4). Combined with EM analysis, these data demonstrate that LRP6-E1E2 and LRP6-E3E4 form two rigid structural blocks, with a short intervening hinge that restrains their relative orientation. The C-terminal domain of DKK1 (DKK1c) interacts with the top surface of the LRP6-E3 YWTD propeller and given their structural similarity, probably also that of the LRP6-E1 propeller, through conserved hydrophobic patches buttressed by a network of salt bridges and hydrogen bonds. Our work provides key insights for understanding LRP5/6 structure and the interaction of LRP5/6 with DKK, as well as for drug discovery.

Experimental investigation and numerical prediction of cavitation incurred on propeller surfaces

Multiple types of cavitation appearing on the surface of a marine propeller when the ship advances with high speed cause the decline of the propeller's performance and/or damages (erosions) to the propeller. Therefore, better understandings of the cavitation formations and the ability to predict them are important to a successful propeller design. This paper presents image results of cavitation incurred on the suction surfaces of a specific propeller and analyzes these images to obtain the statistical parameters of cavitations such as their sizes, locations, and occupied areas. These experimental results are used to evaluate the accuracy of the associated RANS simulations in order to identify issues of turbulence and cavitation models commonly used in such simulations.

프로펠러 압력면 캐비테이션의 초기발생 추정 및 실험 검증

Cavitation phenomena appearing on ship propellers have long been interested and recent theoretical analysises give good results comparing with model tests. In accordance with a continuous rise in heavy powered and high speed ships, hull forms have been changed and loads acting on the propeller surface have also been increased, and they result in various and particular cavitations. In some cases, cavitation appears not only on the back but also on the face of the propeller and it causes additive pressure fluctuations and erosion of the propeller and reduces propulsion efficiency of the ship. In this study, we predict the face cavity inception using unsteady propeller analysis based on the panel method and compare the results with experimental observations.

Structure of the yeast polarity protein Sro7 reveals a SNARE regulatory mechanism

Polarized exocytosis requires coordination between the actin cytoskeleton and the exocytic machinery responsible for fusion of secretory vesicles at specific sites on the plasma membrane. Fusion requires formation of a complex between a vesicle-bound R-SNARE and plasma membrane Qa, Qb and Qc SNARE proteins. Proteins in the lethal giant larvae protein family, including lethal giant larvae and tomosyn in metazoans and Sro7 in yeast, interact with Q-SNAREs and are emerging as key regulators of polarized exocytosis. The crystal structure of Sro7 reveals two seven-bladed WD40 beta-propellers followed by a 60-residue-long 'tail', which is bound to the surface of the amino-terminal propeller. Deletion of the Sro7 tail enables binding to the Qbc SNARE region of Sec9 and this interaction inhibits SNARE complex assembly. The N-terminal domain of Sec9 provides a second, high-affinity Sro7 interaction that is unaffected by the tail. The results suggest that Sro7 acts as an allosteric regulator of exocytosis through interactions with factors that control the tail. Sequence alignments indicate that lethal giant larvae and tomosyn have a two-beta-propeller fold similar to that of Sro7, but only tomosyn appears to retain the regulatory tail.

An evaluation of two inexpensive energy-balance techniques for measuring water use in flood-irrigated pecans ( Carya illinoinensis)

Pecan ( Carya illinoinensis) production in the southwestern US represents a significant proportion of both the irrigated farmland and the consumptive water use of crops. Increasing the irrigation efficiency of pecan orchards is essential to decreasing the amount of water applied while maintaining the productivity of the orchards. In order to increase the irrigation efficiency, it is necessary to measure water use for orchards of different sizes and ages. The most common system uses the sonic eddy covariance (SEC) technique, which utilizes a sonic anemometer and an open path water vapor sensor to measure orchard water use. This method is expensive and can be complicated to instrument, leaving a demand for cheaper and easier methods. The accuracy of two inexpensive micrometeorological systems (energy-balance techniques) were compared to an SEC system by measuring sensible heat flux ( H) and latent heat flux (LE) densities over a mature pecan canopy in the Mesilla Valley of southern NM for two growing seasons. The energy-balance techniques evaluated in this study used one propeller eddy covariance (OPEC) and surface renewal analysis (SR) to measure H and then calculate LE as a residual of the energy balance. SR was evaluated at two measurement heights ( z); canopy height ( h) and the zero plane displacement height d = 0.7 h. Both the SEC and OPEC systems were evaluated at z ∼ 1.3 h. The SEC system measured H and LE using a three-axis sonic anemometer and a fast response, open path, infrared gas analyzer. When the daily total of H was positive, OPEC underestimated H by 13%. When the daily total of H was negative, OPEC overestimated H by 124%. For the daily LE evaluation, the OPEC underestimated LE within 8% for both years. The SR sensor underestimated daily LE by 8% at z = d and overestimated by 11% at z = h for both years. It is recommended that the OPEC system be used with z ≥ ( d + 6) m and a correction factor of 1.13 when daily totals of H are greater than zero, otherwise a correction of 2.24 should be used. The SR system could be used at z = h using an alpha calibration of 0.5 or at z = d with an alpha of 1.1 to calculate LE in this tall, irrigated canopy. On a seasonal basis, the corrected OPEC estimated the water use within an error of 5% (0.06 m) of SEC for both study years, SR at z = d was within 14% (0.17 m) and SR at z = h was within 1% (0.01 m). Using the SR system to measure pecan consumptive water use was simpler to instrument than the OPEC but, it may need to be calibrated on-site by an SEC system negating its usefulness as a stand alone, water use measurement tool. The growing-season crop coefficients ( K c) for orchards like pecan can be measured by OPEC or SR reasonably. Measuring K c by OPEC or SR for winter crops needs to be further tested because these systems overestimated pecan K c in the dormancy seasons. SEC measurements had more ET and K c outliers in the growing seasons than the OPEC and SR systems because SEC ET measurements are not constrained by energy balance. Using the OPEC or SR systems to measure pecan (or other tree crops) water use are accurate and cost-effective methods that can aid crop water and irrigation management.

표면 유선에 정렬된 날개 단면을 이용한 프로펠러 형상 설계

In this paper, we suggest a design concept of defining the propeller geometry by stacking up the blade sections aligned with propeller surface streamlines. Numerical and experimental propeller open water(P.O.W.) characteristics of a newly designed propeller are presented. The surface streamlines for a propeller are obtained by using the panel method. Redefinition of the blade sections aligned with the streamlines is provided together with 8-spline modeling, by which we manufacture model propellers. We carried out the P.O.W, tests in a towing tank in order to show the effect of the present method on P.O.W. characteristics.

Crystal structure of Ski8p, a WD-repeat protein with dual roles in mRNA metabolism and meiotic recombination.

Ski8p is a WD-repeat protein with an essential role for the Ski complex assembly in an exosome-dependent 3'-to-5' mRNA decay. In addition, Ski8p is involved in meiotic recombination by interacting with Spo11p protein. We have determined the crystal structure of Ski8p from Saccharomyces cerevisiae at 2.2 A resolution. The structure reveals that Ski8p folds into a seven-bladed beta propeller. Mapping sequence conservation and hydrophobicities of amino acids on the molecular surface of Ski8p reveals a prominent site on the top surface of the beta propeller, which is most likely involved in mediating interactions of Ski8p with Ski3p and Spo11p. Mutagenesis combined with yeast two-hybrid and GST pull-down assays identified the top surface of the beta propeller as being required for Ski8p binding to Ski3p and Spo11p. The functional implications for Ski8p function in both mRNA decay and meiotic recombination are discussed.