Parametric Study on Hub Vortex Reducing Effects of Propeller Boss Cap Fins by Force and Wake Field Measurements in Open Water and Self-Propulsion Conditions

2016 ◽  
Author(s):  
Jeonghwa Seo ◽  
Bumwoo Han ◽  
Shin Hyung Rhee ◽  
Seung-Jae Lee ◽  
Hyeseong Kim ◽  
...  
Keyword(s):  
Force Measurement ◽  
Field Measurements ◽  
Open Water ◽  
Stereoscopic Particle Image Velocimetry ◽  
Design Parameters ◽  
Total Efficiency ◽  
Wake Field ◽  
Propeller Wake ◽  
Global Force ◽  
Measurement Results

Propeller boss cap fins (PBCF) is one of the most popular ESDs in the industry. The present study aims to investigate effects of design variations of PBCFs on the propulsive efficiency and propeller wake field, with special attention on hub vortex dynamics. The wake fields and force on the whole propulsive system were measured by a towed underwater stereoscopic particle image velocimetry (SPIV) system and a propeller open water (POW) test dynamometer, respectively. Design parameters of PBCFs, i.e., the fin surface area and the angle of attack onto the fins, were varied to control fin loading on the PBCF. In the wake field, root vortices generated from the propeller blades were separated by PBCF and did not form a strong hub vortex, which caused pressure drop on the propeller boss cap. The hub vortex reduction practically increased total thrust, as evidenced in the global force measurement results. In PBCF design variations, Total efficiency increased linearly as the pitch angle and fin chord length decreased. The global force measurement results implied that PBCF in light loading separated root vortices efficiently. Hub vortex reduction by PBCF in light loading was also confirmed by the wake field measurement. In the case of low fin height, however, root vortices were not blocked and actually merged to form a hub vortex. Therefore, the primary function of PBCF, i.e., reducing hub vortex, was not effective anymore and the total efficiency decreased. In heavy loading conditions, axial velocity near the center retarded further, causing greater drag and diminishing the total efficiency. The model tests were also conducted in self propulsion condition, to reveal that the new PBCF with reduced loading also improves the energy saving performance when it works in the wake of the ship.

scholarly journals CFD Analysis on Propeller Performance with Propeller Boss Cap Fin

2019 ◽  
Vol 8 (4) ◽  
pp. 9516-9521
Keyword(s):  
Open Water ◽  
Developed Countries ◽  
Design Parameters ◽  
Propeller Wake ◽  
Water Test ◽  
Shaft Torque ◽  
Dynamic Meshing ◽  
Propeller Performance ◽  
Fuel Consumption And Emissions ◽  
Developing And Developed Countries

The global price of oil, which is both finite and limited in quantity, has been rising steadily because of the increasing requirements for energy in both developing and developed countries. Furthermore, regulations have been strengthened across all industries to address global warming. Many studies of hull resistance, propulsion and operation of ships have been performed to reduce fuel consumption and emissions. The present study examined the design parameters of the propeller boss cap fin (PBCF) and hub cap in improving the propeller efficiency. PBCF is the kind of hydrodynamic energy saving device which aims to reduce energy losses associated with propeller hub vortex by fitting fins to the cap of a propeller. The main principles of PBCF is breaking up hub vortex to straighten propeller wake, thus recovering the negative pressure on the cap. This reduces propeller’s rotational losses and produces negative torque to reduce propeller shaft torque and generating thrust. The study focuses on the size of the blades on boss cap and optimizing its geometry using CFD technique. Open Water Test has been modelled using dynamic meshing technology known as overset meshing. Seven variations of PBCF are modelled and tested to estimate the efficiency of the propeller. The obtained results are then compared with the simulation result with the propeller without PBCF arrangements. The propeller characteristics (without PBCF) has been initially validated using overset meshing strategy with the available experimental results. Overset mesh has been used to perform this analysis to give better control over the fluid flow. It has been observed that, the propeller with PBCF, one among seven variations is giving nearly 2.0% more efficient than the propeller without PBCF.

Influence of Design Parameter Variations for Propeller-Boss-Cap-Fins on Hub Vortex Reduction

2016 ◽  
Vol 60 (04) ◽  
pp. 203-218
Author(s):  
Jeonghwa Seo ◽  
Seung-Jae Lee ◽  
Bumwoo Han ◽  
Shin Hyung Rhee
Keyword(s):  
Pitch Angle ◽  
Design Parameter ◽  
Open Water ◽  
Chord Length ◽  
Stereoscopic Particle Image Velocimetry ◽  
Design Parameters ◽  
Phase Lag ◽  
Water Efficiency ◽  
Parameter Variations ◽  
Wake Fields

The present study aimed to identify significant design parameters on the propeller open water efficiency and characteristics of the wake field of a propeller with propeller-boss-cap-fins (PBCFs), with special attention to hub vortex dynamics. A towed underwater stereoscopic particle image velocimetry system was used to measure the near wake fields of a five-bladed propeller and a PBCF model. Through model tests, it was confirmed that the disappearance of a low-pressure area behind a boss cap, i.e., a reduction of the hub vortex, was the dominant contribution to open water efficiency gains from PBCF rather than a decrease in net torque. Global force and wake fields were also measured in response to design parameter variations of PBCF, i.e., fin chord length, fin span height, pitch angle, and phase lag. In the cases of pitch angle and fin chord length variations, PBCF with a light loading configuration had better open water efficiency than the baseline PBCF. However, in the case of a short fin span height for light loading configuration, the hub vortex was not entirely prevented, and the total open water efficiency decreased. Under heavy loading configurations, excessive negative and torque degraded the open water efficiency. Phase lag variations were less effective with respect to the open water efficiency than other design parameter variations.

Design of a compact UWB antenna with a partial ground plane on epoxy woven glass material

2017 ◽  
Vol 24 (1) ◽  
pp. 73-79
Author(s):  
Md. Moinul Islam ◽  
Mohammad Tariqul Islam ◽  
Mohammad Rashed Iqbal Faruque ◽  
Rabah W. Aldhaheri ◽  
Md. Samsuzzaman
Keyword(s):  
Dielectric Material ◽  
Ground Plane ◽  
Ultra Wideband ◽  
Design Parameters ◽  
Uwb Antenna ◽  
Glass Material ◽  
Measurement Results ◽  
Good Term ◽  
Parametric Analyses ◽  
Uwb Applications

AbstractA compact ultra-wideband (UWB) antenna is presented in this paper with a partial ground plane on epoxy woven glass material. The study is discussed to comprehend the effects of various design parameters with explicit parametric analyses. The overall antenna dimension is 0.22×0.26×0.016 λ. A prototype is made on epoxide woven glass fabric dielectric material of 1.6 mm thickness. The measured results point out that the reported antenna belongs to a wide bandwidth comprehending from 3 GHz to more than 11 GHz with VSWR<2. It has a peak gain of 5.52 dBi, where 3.98 dBi is the average gain. Nearly omnidirectional radiation patterns are observed within the operating frequency bands. A good term exists between simulation and measurement results, which lead the reported antenna to be an appropriate candidate for UWB applications.

Green roof hydrologic performance and modeling: a review

2013 ◽  
Vol 69 (4) ◽  
pp. 727-738 ◽  
Author(s):  
Yanling Li ◽  
Roger W. Babcock
Keyword(s):  
Peak Flow ◽  
Green Roof ◽  
Field Measurements ◽  
Green Roofs ◽  
Economic Benefits ◽  
Design Parameters ◽  
Technical Literature ◽  
Factors Affecting ◽  
Model Soil ◽  
Runoff Volume

Green roofs reduce runoff from impervious surfaces in urban development. This paper reviews the technical literature on green roof hydrology. Laboratory experiments and field measurements have shown that green roofs can reduce stormwater runoff volume by 30 to 86%, reduce peak flow rate by 22 to 93% and delay the peak flow by 0 to 30 min and thereby decrease pollution, flooding and erosion during precipitation events. However, the effectiveness can vary substantially due to design characteristics making performance predictions difficult. Evaluation of the most recently published study findings indicates that the major factors affecting green roof hydrology are precipitation volume, precipitation dynamics, antecedent conditions, growth medium, plant species, and roof slope. This paper also evaluates the computer models commonly used to simulate hydrologic processes for green roofs, including stormwater management model, soil water atmosphere and plant, SWMS-2D, HYDRUS, and other models that are shown to be effective for predicting precipitation response and economic benefits. The review findings indicate that green roofs are effective for reduction of runoff volume and peak flow, and delay of peak flow, however, no tool or model is available to predict expected performance for any given anticipated system based on design parameters that directly affect green roof hydrology.

scholarly journals On contribution of horizontal and intra-layer convection to the formation of the Baltic Sea cold intermediate layer

2008 ◽  
Vol 5 (4) ◽  
pp. 581-623
Author(s):  
I. P. Chubarenko ◽  
N. Y. Demchenko
Keyword(s):  
Baltic Sea ◽  
Intermediate Layer ◽  
Heat Content ◽  
Field Measurements ◽  
Open Water ◽  
Early Spring ◽  
Cold Intermediate Layer ◽  
The Baltic Sea ◽  
The Baltic ◽  
Fast Increase

Abstract. Seasonal cascades down the coastal slopes and intra-layer convection are considered as the two mechanisms contributing to the Baltic Sea cold intermediate layer (CIL) formation. On the base of TS-diagrams, mean-annual and real-time temperature profiles, the CIL features are re-analyzed. The presence within the CIL of water with temperature below that of maximum density (Tmd) and that at the local surface allows tracing its formation. Field measurements are presented, showing specific features of denser water formation in marine environment. It is argued that such cascades formed during early spring heating (March–April) – before reaching the Tmd – are the source of the coldest waters of the CIL. Fast increase of the open water heat content during further spring heating indicates that horizontal exchange rather than direct solar heating is responsible for that. When the surface is covered with water, heated above the Tmd, the conditions within the CIL become favorable for intralayer convection due to the presence of waters of Tmd in intermediate layer, which can explain the observed increase of its salinity and deepening with time.

scholarly journals Near-Field Antenna Measurements with Manual Collection of the Measurement Samples

2020 ◽  
Vol 18 ◽  
pp. 17-22
Author(s):  
Fabian T. Faul ◽  
Hans-Jürgen Steiner ◽  
Thomas F. Eibert
Keyword(s):  
Near Field ◽  
Field Measurements ◽  
Controlled Environment ◽  
Positioning System ◽  
Probe Position ◽  
Site Testing ◽  
Error Level ◽  
Measurement Results ◽  
Anechoic Chambers ◽  
Chamber Measurements

Abstract. Near-field measurements are commonly performed in anechoic chambers which limits the flexibility of the measurements and requires high precision equipment to achieve exact results. In this contribution, we investigate a simple near-field measurement setup which does not use any sophisticated positioning system nor operates in a controlled environment. Instead, the probe antenna is moved by an operator person while the probe position is measured by a laser tracker. This implies that the measurement results will have a higher error level in comparison with antenna chamber measurements. However, excellent error levels are not always necessary, especially when it comes to on-site testing of the principle functionality of antennas. Measurement results are shown to illustrate the performance of the system.

Sensitivity Analysis for the Operating Efficiency of an Axial Piston Pump

2015 ◽  
Author(s):  
Noah D. Manring ◽  
Viral S. Mehta ◽  
Jeff L. Kuehn ◽  
Bryan E. Nelson
Keyword(s):  
Power Efficiency ◽  
Design Parameters ◽  
Operating Efficiency ◽  
Parameter Study ◽  
Total Efficiency ◽  
Pump Efficiency ◽  
Large Set ◽  
Algebraic Equations ◽  
Pump Design ◽  
Axial Piston

Axial piston pumps of swash-plate type are extensively used in off-highway machines to convert rotating mechanical power into hydraulic power. Efficiency of such pumps is of considerable importance to hydraulic design engineers. Many researchers have tried to create mathematical models for describing pump efficiency. These models are typically a system of nonlinear algebraic equations dependent upon a total of four variables (pressure, speed, temperature, displacement) and a set of experimentally determined coefficients. Since these models are not of the a-priori type, they are not of much value to a design engineer who is trying to design an efficient pump. Others have tried to use physics based models and numerical programs to accurately predict the influence of component design on efficiency. Such programs are considerably slow to run and of not much use to a design engineer who needs to make quick decisions. Hence the objective of this paper is to understand the sensitivity of various design parameters on the total efficiency of the pump by conducting a dimensionless parameter study of a large set of pump design parameters. Using this method it will be shown that a small group of design parameters have the highest influence on the efficiency of these pumps.

scholarly journals Measurement-based modeling of daytime and nighttime oxidation of atmospheric mercury

2017 ◽  
Author(s):  
Maor Gabay ◽  
Mordechai Peleg ◽  
Erick Fredj ◽  
Eran Tas
Keyword(s):  
Lower Limit ◽  
Rate Constant ◽  
Field Measurements ◽  
Elemental Mercury ◽  
Chemical Oxidation ◽  
Atmospheric Mercury ◽  
Gaseous Elemental Mercury ◽  
Measurement Results ◽  
Kinetic Calculations ◽  
First Time

Abstract. Accurate characterization of gaseous elemental mercury (GEM) chemical oxidation pathways and their kinetics is critically important for assessing the transfer of atmospheric mercury to bioaquatic systems. Recent comprehensive field measurements have suggested that the nitrate radical (NO3) plays a role in efficient nighttime oxidation of GEM, and that the role of the hydroxyl radical (OH) as a GEM oxidant has been underestimated. We used the CAABA/MECCA chemical box model and additional kinetic calculations to analyze these measurement results, in order to investigate the nighttime and daytime oxidation of GEM. We assumed a second-order reaction for the NO3 induced nighttime oxidation of GEM. Our analysis demonstrated that nighttime oxidation of GEM has to be included in the model to account for the measured variations in nighttime reactive gaseous mercury (RGM) concentration. A lower limit and best-fit rate constant for GEM nighttime oxidation are provided. To the best of our knowledge, this is the first time that a rate for nighttime oxidation of GEM has been determined based on field measurements. Our analysis further indicates that OH has a much more important role in GEM oxidation than commonly considered. A lower-limit rate constant for the OH–RGM reaction is provided.

scholarly journals Measuring Hydrometeors with a Precipitation Microphysical Characteristics Sensor: Calibration and Field Measurements

2017 ◽  
Vol 2017 ◽  
pp. 1-16 ◽  
Author(s):  
Yuntao Hu ◽  
Xichuan Liu ◽  
Taichang Gao ◽  
Xiaojian Shu
Keyword(s):  
Field Measurements ◽  
Rain Gauge ◽  
Sensor Calibration ◽  
Threshold Method ◽  
Fall Velocity ◽  
Axis Ratio ◽  
Measurement Results ◽  
Accumulated Rainfall ◽  
Typical Shape ◽  
Particle Imaging

Aiming at the simultaneous measurement of the size, shape, and fall velocity of precipitation particles in the natural environment, we present here a new ground-based precipitation microphysical characteristics sensor (PMCS) based on the particle imaging velocimetry technology. The PMCS can capture autocorrelated images of precipitation particles by double-exposure in one frame, by which the size, axis ratio, and fall velocity of precipitation particles can be calculated. The PMCS is calibrated by a series of glass balls with certain diameters under varying light conditions, and a self-adaptive threshold method is proposed. The shape, axis ratio, and fall velocity of raindrops were calculated and discussed based on the field measurement results of PMCS. The typical shape of large raindrop is an oblate ellipsoid, the axis ratio of raindrops decreases linearly with the diameter, the fall velocity of raindrops approaches its asymptote, and the above observed results are in good agreement with the empirical models; the synchronous observation of a PMCS, an OTT PARSIVEL disdrometer, and a rain gauge shows that the PMCS is able to measure the rain intensity, accumulated rainfall, and drop size distribution with high accuracy. These results have validated the performance of PMCS.

Coastal Engineering Analysis, Field Measurements, Numerical Modeling and Design for the Optimized Extension of the Beach in Ras Al-Ardh Area, Salmiya, Kuwait

2019 ◽  
Author(s):  
S. Neelamani ◽  
Bassam N. Shuhaibar ◽  
Khaled Al-Salem ◽  
Yousef Al-Osairi ◽  
Qusaie E. Karam ◽  
...  
Keyword(s):  
Numerical Modeling ◽  
Sandy Beach ◽  
Field Measurements ◽  
Beach Nourishment ◽  
Beach Sand ◽  
Design Parameters ◽  
Model Study ◽  
Sea Bed ◽  
Waves And Currents ◽  
Tourism Enterprises

Abstract Maintaining and retaining a quality sandy beach is a primary requirement for attracting people and tourists in any coastal country. Tourism Enterprises Company (TEC) in Kuwait owns 230 m long sandy beach in Ras Al-Ardh Sea Club, Salmiya, Kuwait. The beach has been eroding because of strong hydrodynamics forces from waves and currents. TEC wants to develop a stable sandy beach of 30 m wide. Kuwait Institute for Scientific Research (KISR), Kuwait is assigned to carry out the required scientific studies. In order to make sure a stable quality beach will exist, KISR has carried out the needed studies, which involves the field measurements such as bbathymetry survey, current and tidal variations, physical characteristics of beach soil, beach and sea bed profile, establishing the design parameters such as waves, currents, tide and wind. Hydrodynamic model study using DELFT3D model for the present and for the proposed extended groin conditions with beach nourishment were carried out. Also numerical modeling using GENESIS model to understand the future shore line changes due to the proposed development was carried out. Design of Groins to estimate the weight of armor units and weight of inner layers were carried out. The particle size and quantity of sand needed for reclamation of 30 m wide beach was estimated. Based on the study, it is recommended that the sandy soil to be used for 30 m wide beach nourishment should have D50 greater than 0.42 mm (say 0.5 mm) and D10 greater than 0.25 mm. The borrow pit much be selected by keeping this soil characters in mind. It is recommended to use a submerged offshore breakwater in order to retain the beach sand in place and for reducing the maintenance nourishment. Otherwise, large quantity of the capital nourished beach sand will escape into the deeper water due to strong current coupled with waves and steep seabed slopes. Environmental Impact Study was carried out as per Kuwait Environment Public Authority requirements to bring out the impacts due to beach filling and the construction submerged offshore barrier and extension of east groin for a distance of 30 m. TEC will implement the recommendations for developing the beach in Ras Al-Ardh sea club and will be useful to attract more people to use this beach.

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