Noise investigation of a cavitating orifice: use of cfd simulation and ffowcs williams–hawkings (fw-h) formulation to gain insight into acoustics condition

In the present work, the mean flow field in a stirred tank equipped with a scale model of a commercially available Grundfos AFG.40.230.35 flowmaker is investigated using CFD simulation and Laser Doppler Anemometry (LDA), in order to provide information on the interaction between flow, propeller and wall proximity. The propeller is placed at a specified location in the tank, and measurements are taken at various locations in the tank to provide as detailed a representation of the resulting flow as possible as well as insight into the near-field of the flowmaker. The simulation, carried out with Ansys CFX 10, used a multiple frame of reference (MFR) approach to include a full representation of the flowmaker blade and motor geometry, to fully include the effects of the blade shape and variable pitch. The reported results are based on a k-e model using a second order discretization scheme. The results show good agreement on downstream axial velocities immediately after the flowmaker, although the numerical results exhibit symmetry to a greater extent than the experimental data, which is believed to be due to a combination of wall proximity effects in the latter and the turbulence model in the latter. However, the results provide valuable insight into the performance of CFD analysis on this type of flow maker, and highlight aspects for future work.

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Investigation of Ventilation and Current Effect of Tunnel Thruster for DP Applications

Volume 1: Offshore Technology; Offshore Geotechnics ◽

10.1115/omae2015-42127 ◽

2015 ◽

Author(s):

Ping Lu ◽

Sue Wang

Keyword(s):

North Sea ◽

Cfd Simulation ◽

Present Knowledge ◽

Dynamic Positioning ◽

Propeller Shaft ◽

Current Effect ◽

Allocation Algorithms ◽

Thrust Allocation ◽

Insight Into ◽

Ship Speed

This paper presents a CFD simulation to study the ventilation phenomenon of tunnel thrusters in dynamic positioning (DP) mode of a typical North Sea shuttle tanker consisting of two main propellers, two rudders, and two bow tunnel thrusters. Measurements of blade thrust and moment for the propeller shaft (corresponding to propeller torque) with ventilated propellers at different submersion positions are presented and discussed. Additionally, in order to obtain insight into the effect of waves on ventilation which further affects propeller loading and dynamic fluctuations, simulations of a tunnel thruster are performed at different immersion ratios. This paper also presents and discusses the factors in the evaluation of thruster performance, such as, the extent of present knowledge for tunnel thrusters as related to ahead ship speed, and interaction between thruster jet flow and the mainstream with various drift angles. Moreover, thrust degradation of tunnel thrusters is considered in the thrust allocation algorithms for the DP capability calculation. The objective of this study is to understand the dynamics of thruster forces. In addition, results of the study provide knowledge for a robust thrust allocation algorithm for dynamic positioning capability assessment.

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Assessment of downward draught in high-glazing facades in cold climates – experimental and CFD study into draught control with a 21-type radiator

E3S Web of Conferences ◽

10.1051/e3sconf/202124602002 ◽

2021 ◽

Vol 246 ◽

pp. 02002

Author(s):

Karl-Villem Võsa ◽

Andrea Ferrantelli ◽

Jarek Kurnitski

Keyword(s):

Cfd Simulation ◽

Standardized Test ◽

Test Chamber ◽

Thermal Plume ◽

Cold Climates ◽

Experimental Phase ◽

High Fraction ◽

Typical Solution ◽

Partial Loads ◽

Insight Into

This paper investigates the interaction of a radiator’s thermal plume and downdraught of cold glazed surfaces. Draughts in working areas are one of the most common thermal comfort complaints in modern buildings. A typical solution for dealing with these draughts is positioning the heat emitters such as radiators or convectors under the windows. However, with thermally efficient envelopes, the internal loads compromise a relatively high fraction of the heating demand and the emitters are working under partial loads in modern buildings. This study comprises two parts: an experimental phase in the EN442 standardized test chamber with a 21-type radiator, and a CFD simulation phase, where the model is validated and applied under an expanded set of boundary conditions. The expanded simulation set results provide preliminary insight into sizing and design. More specifically, the thermal plume can be parametrised with a velocity and temperature value along with the room air and glazing temperatures for a broader analysis and assessment of the risk of draught.

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Calibration problems in hydrogen luminosities

Symposium - International Astronomical Union ◽

10.1017/s0074180900053626 ◽

1966 ◽

Vol 24 ◽

pp. 322-330

Author(s):

A. Beer

Keyword(s):

Galactic Structure ◽

B Stars ◽

Insight Into

The investigations which I should like to summarize in this paper concern recent photo-electric luminosity determinations of O and B stars. Their final aim has been the derivation of new stellar distances, and some insight into certain patterns of galactic structure.

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Stochasting modeling of planetary ring systems

International Astronomical Union Colloquium ◽

10.1017/s025292110010154x ◽

1984 ◽

Vol 75 ◽

pp. 461-469 ◽

Cited By ~ 1

Author(s):

Robert W. Hart

Keyword(s):

Maximum Entropy ◽

Ring System ◽

The Sun ◽

Ultimate State ◽

Interparticle Interactions ◽

Ring Systems ◽

First Order ◽

Planetary Ring ◽

Insight Into

ABSTRACTThis paper models maximum entropy configurations of idealized gravitational ring systems. Such configurations are of interest because systems generally evolve toward an ultimate state of maximum randomness. For simplicity, attention is confined to ultimate states for which interparticle interactions are no longer of first order importance. The planets, in their orbits about the sun, are one example of such a ring system. The extent to which the present approximation yields insight into ring systems such as Saturn's is explored briefly.

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Skeletal elements of crinoid echinoderms: High-resolution structural and microanalytical results

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100074768 ◽

1983 ◽

Vol 41 ◽

pp. 194-195

Author(s):

D. F. Blake ◽

L. F. Allard ◽

D. R. Peacor

Keyword(s):

High Resolution ◽

Marine Invertebrates ◽

Sea Urchins ◽

Structural Features ◽

Sea Stars ◽

High Resolution Tem ◽

Relationship Of ◽

The Relationship ◽

Insight Into

Echinodermata is a phylum of marine invertebrates which has been extant since Cambrian time (c.a. 500 m.y. before the present). Modern examples of echinoderms include sea urchins, sea stars, and sea lilies (crinoids). The endoskeletons of echinoderms are composed of plates or ossicles (Fig. 1) which are with few exceptions, porous, single crystals of high-magnesian calcite. Despite their single crystal nature, fracture surfaces do not exhibit the near-perfect {10.4} cleavage characteristic of inorganic calcite. This paradoxical mix of biogenic and inorganic features has prompted much recent work on echinoderm skeletal crystallography. Furthermore, fossil echinoderm hard parts comprise a volumetrically significant portion of some marine limestones sequences. The ultrastructural and microchemical characterization of modern skeletal material should lend insight into: 1). The nature of the biogenic processes involved, for example, the relationship of Mg heterogeneity to morphological and structural features in modern echinoderm material, and 2). The nature of the diagenetic changes undergone by their ancient, fossilized counterparts. In this study, high resolution TEM (HRTEM), high voltage TEM (HVTEM), and STEM microanalysis are used to characterize tha ultrastructural and microchemical composition of skeletal elements of the modern crinoid Neocrinus blakei.

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Structure and function of neural networks in the retina

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100102213 ◽

1988 ◽

Vol 46 ◽

pp. 26-27

Author(s):

Peter Sterling

Keyword(s):

Ganglion Cells ◽

Three Dimensional ◽

Structure And Function ◽

Synaptic Connections ◽

Visual Axis ◽

One Dimensional ◽

Cat Retina ◽

Ultrathin Sections ◽

And Function ◽

Insight Into

The synaptic connections in cat retina that link photoreceptors to ganglion cells have been analyzed quantitatively. Our approach has been to prepare serial, ultrathin sections and photograph en montage at low magnification (˜2000X) in the electron microscope. Six series, 100-300 sections long, have been prepared over the last decade. They derive from different cats but always from the same region of retina, about one degree from the center of the visual axis. The material has been analyzed by reconstructing adjacent neurons in each array and then identifying systematically the synaptic connections between arrays. Most reconstructions were done manually by tracing the outlines of processes in successive sections onto acetate sheets aligned on a cartoonist's jig. The tracings were then digitized, stacked by computer, and printed with the hidden lines removed. The results have provided rather than the usual one-dimensional account of pathways, a three-dimensional account of circuits. From this has emerged insight into the functional architecture.

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Radiation Damage Studies with the HVEM

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100096655 ◽

1972 ◽

Vol 30 ◽

pp. 680-681

Author(s):

J. J. Laidler ◽

B. Mastel

Keyword(s):

Radiation Damage ◽

Stainless Steels ◽

Volume Expansion ◽

Austenitic Stainless Steels ◽

Test Facility ◽

Fast Breeder Reactors ◽

Breeder Reactors ◽

Under Construction ◽

Development Laboratory ◽

Insight Into

One of the major materials problems encountered in the development of fast breeder reactors for commercial power generation is the phenomenon of swelling in core structural components and fuel cladding. This volume expansion, which is due to the retention of lattice vacancies by agglomeration into large polyhedral clusters (voids), may amount to ten percent or greater at goal fluences in some austenitic stainless steels. From a design standpoint, this is an undesirable situation, and it is necessary to obtain experimental confirmation that such excessive volume expansion will not occur in materials selected for core applications in the Fast Flux Test Facility, the prototypic LMFBR now under construction at the Hanford Engineering Development Laboratory (HEDL). The HEDL JEM-1000 1 MeV electron microscope is being used to provide an insight into trends of radiation damage accumulation in stainless steels, since it is possible to produce atom displacements at an accelerated rate with 1 MeV electrons, while the specimen is under continuous observation.

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