Effect of Compressibility on Peak Impact Pressure and Pressure Distribution During Water Entry of a Wedge

2015 ◽  
Author(s):  
Yi Zhang ◽  
Ali Mohtat ◽  
Solomon C. Yim
Keyword(s):  
Mach Number ◽  
Sound Speed ◽  
Numerical Study ◽  
Pressure Coefficient ◽  
Water Entry ◽  
Impact Pressure ◽  
Speed Ratio ◽  
Wave Impact ◽  
Entry Velocity ◽  
Fluid Compressibility

Ship hull slamming and wave impact on wave energy converters (WEC) are an important problem in naval architecture and marine hydrokinetic for the survivability of vessels and WECs in adverse environmental conditions. An idealized canonical model for these problems can be traced back to the water entry of a wedge–shaped rigid object. Common asymptotic and empirical models are often based on the assumption that the fluid is incompressible and the initial wedge entry velocity to sound speed ratio (defined as the characterized Mach number) is low. In this paper, we present some initial results of a numerical study of the effect of fluid compressibility on the peak slamming impact pressure. The deadrise angle and entry velocity of the model are varied to examine the sensitivity of the peak and distribution of the pressure response with respect to these parameters. The fluid compressibility is controlled through the bulk modulus and manifested as various sound speeds. The normalization using this sound speed shows that the pressure coefficient changes consistently for a certain deadrise angle. The results indicates that despite a low Mach number, the fluid compressibility in the numerical model affects the peak pressure significantly, implying an overestimation in engineering application by the classical asymptotic incompressible theory.

scholarly journals Numerical Assessment of Similitude Parameters and Dimensional Analysis for Water Entry Problems

2015 ◽  
Vol 2015 ◽  
pp. 1-15 ◽  
Author(s):  
Andrea L. Facci ◽  
Stefano Ubertini
Keyword(s):  
Numerical Study ◽  
Computational Study ◽  
Water Entry ◽  
Laboratory Scale ◽  
Analytical Models ◽  
Experimental Investigations ◽  
Two Dimensional ◽  
Wide Range ◽  
Entry Velocity ◽  
Real Size

The prediction of impulsive loads deriving from the sudden impact of a solid body on the water surface is of fundamental importance for a wide range of engineering applications. The study of hull-slamming phenomena largely relies on laboratory scale experimental investigations and on simplified analytical models. The aim of this paper is to quantitatively assess the interplay between the relevant nondimensional parameters for the water entry of a two-dimensional body, evidencing the similitude conditions that allow the transition from scaled experiments to real size applications. This assessment is performed through the numerical study of the hydrodynamics induced by the water impact of a two-dimensional wedge. The fluid flow is considered incompressible. First of all numerical simulations are validated by comparison with experimental data from the literature and with the Wagner seminal theory. Afterwards, a thorough computational study is performed by systematically varying all the relevant parameters, such as the nondimensional entry velocity and acceleration. We conclude by evidencing some design prescriptions that should be adopted in order to facilitate the transition of laboratory scale experiments to real scale applications.

Numerical investigations on the effect of volute casing treatment for performance augmentation in a centrifugal fan

2021 ◽  
pp. 095440622110341
Author(s):  
Manjunath L Nilugal ◽  
K Vasudeva Karanth ◽  
Madhwesh N
Keyword(s):  
Total Pressure ◽  
Static Pressure ◽  
Numerical Study ◽  
Pressure Coefficient ◽  
Three Dimensional ◽  
Pressure Rise ◽  
Centrifugal Fan ◽  
Casing Treatment ◽  
Sliding Mesh ◽  
Optimum Configuration

This article presents the effect of volute chamfering on the performance of a forward swept centrifugal fan. The numerical analysis is performed to obtain the performance parameters such as static pressure rise coefficient and total pressure coefficient for various flow coefficients. The chamfer ratio for the volute is optimized parametrically by providing a chamfer on either side of the volute. The influence of the chamfer ratio on the three dimensional flow domain was investigated numerically. The simulation is carried out using Re-Normalisation Group (RNG) k-[Formula: see text] turbulence model. The transient simulation of the fan system is done using standard sliding mesh method available in Fluent. It is found from the analysis that, configuration with chamfer ratio of 4.4 is found be the optimum configuration in terms of better performance characteristics. On an average, this optimum configuration provides improvement of about 6.3% in static pressure rise coefficient when compared to the base model. This optimized chamfer configuration also gives a higher total pressure coefficient of about 3% validating the augmentation in static pressure rise coefficient with respect to the base model. Hence, this numerical study establishes the effectiveness of optimally providing volute chamfer on the overall performance improvement of forward bladed centrifugal fan.

scholarly journals Numerical Study on Damage Zones Induced by Excavation and Ventilation in a High-Temperature Tunnel at Depth

Energies ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 4773
Author(s):  
Jianyu Li ◽  
Hong Li ◽  
Zheming Zhu ◽  
Ye Tao ◽  
Chun’an Tang
Keyword(s):  
High Temperature ◽  
Lateral Pressure ◽  
Numerical Study ◽  
Pressure Coefficient ◽  
Fracture Morphology ◽  
In Situ Stress ◽  
Surrounding Rock ◽  
Geothermal System ◽  
Mechanical Coupling ◽  
Lateral Pressure Coefficient

Geothermal power is being regarded as depending on techniques derived from hydrocarbon production in worldwide current strategy. However, it has artificially been developed far less than its natural potentials due to technical restrictions. This paper introduces the Enhanced Geothermal System based on Excavation (EGS-E), which is an innovative scheme of geothermal energy extraction. Then, based on cohesion-weakening-friction-strengthening model (CWFS) and literature investigation of granite test at high temperature, the initiation, propagation of excavation damaged zones (EDZs) under unloading and the EDZs scale in EGS-E closed to hydrostatic pressure state is studied. Finally, we have a discussion about the further evolution of surrounding rock stress and EDZs during ventilation is studied by thermal-mechanical coupling. The results show that the influence of high temperature damage on the mechanical parameters of granite should be considered; Lateral pressure coefficient affects the fracture morphology and scale of tunnel surrounding rock, and EDZs area is larger when the lateral pressure coefficient is 1.0 or 1.2; Ventilation of high temperature and high in-situ stress tunnel have a significant effect on the EDZs scale; Additional tensile stress is generated in the shallow of tunnel surrounding rock, and the compressive stress concentration transfers to the deep. EDZs experiences three expansion stages of slow, rapid and deceleration with cooling time, and the thermal insulation layer prolongs the slow growth stage.

scholarly journals Enhanced predictions of wave impact pressure by improved incompressible SPH methods

2009 ◽  
Vol 31 (2) ◽  
pp. 111-131 ◽  
Author(s):  
Abbas Khayyer ◽  
Hitoshi Gotoh ◽  
Songdong Shao
Keyword(s):  
Impact Pressure ◽  
Wave Impact ◽  
Incompressible Sph

Aerodynamic optimisation of the rocket plane in subsonic and supersonic flight conditions

2017 ◽  
Vol 231 (12) ◽  
pp. 2266-2281 ◽  
Author(s):  
Marcin Figat ◽  
Agnieszka Kwiek
Keyword(s):  
Mach Number ◽  
Main Part ◽  
Numerical Study ◽  
Aerodynamic Characteristics ◽  
Aerodynamic Design ◽  
Supersonic Speed ◽  
Supersonic Flight ◽  
Special Vehicle ◽  
Speed Regime ◽  
The Impact

This paper presents the results of a numerical study of the aerodynamic shape of the Rocket Plane LEX. The Rocket Plane is a main part of the Modular Airplane System – MAS; a special vehicle devoted to suborbital tourist flights. The Rocket Plane was designed for subsonic and supersonic flight conditions. Therefore, the impact of the Mach number should be considered during the aerodynamic design of the Rocket Plane. The main goal of the investigation was to determine the sensitivity of the Rocket Plane aerodynamic characteristics to the Mach number during the optimisation of the LEX geometry. The paper includes results of the optimisation process for Mach number from the range Ma = 0.5 to Ma = 2.5. These results reveal that the aerodynamic characteristics of models optimised for the subsonic and transonic regime of Mach numbers (up to Ma = 1) were also improved for the supersonic speed regime. However, in the case of models optimised for the supersonic flight regime the aerodynamic characteristics in subsonic flight regime, are inferior compared to the model before the optimisation process.

Arriving at the Optimum Overlap Ratio for an Elliptical-Bladed Savonius Rotor

2017 ◽  
Author(s):  
Nur Alom ◽  
Ujjwal K. Saha
Keyword(s):  
Numerical Study ◽  
Superior Performance ◽  
Navier Stokes ◽  
Speed Ratio ◽  
Small Scale ◽  
Efficient Manner ◽  
Ansys Fluent ◽  
Savonius Rotor ◽  
Velocity Magnitude ◽  
Overlap Ratio

The Savonius rotor appears to be particularly promising for the small-scale applications because of its design simplicity, good starting ability, and insensitivity to wind directions. There has been a growing interest in recent times to harness wind energy in an efficient manner by developing newer blade profiles of Savonius rotor. The overlap ratio (OR), one of the important geometric parameters, plays a crucial role in the turbine performance. In a recent study, an elliptical blade profile with a sectional cut angle (θ) of 47.5° has demonstrated its superior performance when set at an OR = 0.20. However, this value of OR is ideal for a semicircular profile, and therefore, requires further investigation to arrive at the optimum overlap ratio for the elliptical profile. In view of this, the present study attempts to make a systemic numerical study to arrive at the optimum OR of the elliptical profile having sectional cut angle, θ = 47.5°. The 2D unsteady simulation is carried out around the elliptical profile considering various overlap ratios in the range of 0.0 to 0.30. The continuity, unsteady Reynolds Averaged Navier-Stokes (URANS) equations and two equation eddy viscosity SST (Shear Stress transport) k-ω model are solved by using the commercial finite volume method (FVM) based solver ANSYS Fluent. The torque and power coefficients are calculated as a function of tip speed ratio (TSR) and at rotating conditions. The total pressure, velocity magnitude and turbulence intensity contours are obtained and analyzed to arrive at the intended objective. The numerical simulation demonstrates an improved performance of the elliptical profile at an OR = 0.15.

Spectral Analysis of Irregular Wave Impact on the Structure in Splash Zone

2002 ◽  
Author(s):  
Bing Ren ◽  
Yongxue Wang
Keyword(s):  
Spectral Analysis ◽  
Wave Height ◽  
Incident Wave ◽  
Impact Pressure ◽  
Splash Zone ◽  
Spectral Moment ◽  
Wave Impact ◽  
Large Wave ◽  
Irregular Wave ◽  
The Impact

The spectral analysis from experimental data of irregular wave impact on the structures with large dimension in the splash zone is presented. The experiments were conducted in the large wave-current tank in the State Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology. In the experiment, the target spectrum is JONSWAP spectrum, the significant wave height H1/3 is in the range from 0.1m to 0.3m, and the peak period of spectrum Tp in the range from 1.0s to 2.0s. The ratio of s/H1/3, which refers to the clearance of the subface of the structure above still water level (s) to the incident wave height, is between −0.1 and 0.4. The spectral analysis results of the irregular wave impact pressure on the subface of the structure under various case studies are presented. The distribution of spectral moment of the impact pressure on the structure along the subface is given. And the influence of different incident wave parameters and relative clearance s/H1/3 on the average spectral moment of impact pressure are discussed.

Numerical analysis of supersonic co-flow jet with varying lip thickness

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Sathish Kumar K ◽  
Naren Shankar R ◽  
Anusindhiya K ◽  
Senthil Kumar B.R
Keyword(s):  
Mach Number ◽  
Total Pressure ◽  
Numerical Study ◽  
Pressure Ratio ◽  
Supersonic Nozzle ◽  
Experimental Result ◽  
Content Type ◽  
Jet Mixing ◽  
Mixing Characteristics ◽  
Jet Axis

Purpose This study aims to present the numerical study on supersonic jet mixing characteristics of the co-flow jet by varying lip thickness (LT). The LT chosen for the study is 2 mm, 7.75 mm and 15 mm. Design/methodology/approach The primary nozzle is designed for delivering Mach 2.0 jet, whereas the secondary nozzle is designed for delivering Mach 1.6 jet. The Nozzle pressure ratio chosen for the study is 3 and 5. To study the mixing characteristics of the co-flow jet, total pressure and Mach number measurements were taken along and normal to the jet axis. To validate the numerical results, the numerical total pressure values were also compared with the experimental result and it is proven to have a good agreement. Findings The results exhibit that, the 2 mm lip is shear dominant. The 7.75 mm and 15 mm lip is wake dominant. The jet interaction along the jet axis was also studied using the contours of total pressure, Mach number, turbulent kinetic energy and density gradient. The radial Mach number contours at the various axial location of the jet was also studied. Practical implications The effect of varying LT in exhaust nozzle plays a vital role in supersonic turbofan aircraft. Originality/value Supersonic co-flowing jet mixing effectiveness by varying the LT between the primary supersonic nozzle and the secondary supersonic nozzle has not been analyzed in the past.

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