Experimentally Measured Hydroelastic Effects on Impact-Induced Loads during Flat Water Entry and Related Uncertainties

2019 ◽  
pp. 1-30
Author(s):  
Simon Toedter ◽  
Ould el Moctar ◽  
Jens Neugebauer ◽  
Thomas E. Schellin
Keyword(s):  
High Speed ◽  
Water Entry ◽  
Test Case ◽  
Primary Concern ◽  
Air Trapping ◽  
Flat Bottom ◽  
Benchmark Data ◽  
Elastic Bottom ◽  
Structural Deformations ◽  
Two Bodies

Abstract Extensive water entry experiments were performed to identify uncertainties associated with measured impact-induced loads acting on flat bottom ship structures. Of primary concern was the influence of air trapping on elastic structural deformations. The experimental measurements supplied benchmark data suitable to validate CFD predictions. Two bodies were tested. One body was fitted with stiffened, rigid bottom plating; the other body, with thin elastic plating. A large number of 30 repetitive runs recorded bottom pressures and forces acting on the flat bottom plating and monitored impact-induced elastic bottom strains. For each test case, high-speed videos of water entry sequences were evaluated. The resulting average peak values standard deviations quantified the uncertainty of these measurements.

Experimental Investigations of Hydroelastic Effects on Loads During Flat Water Entry

2018 ◽  
Author(s):  
Simon Toedter ◽  
Ould el Moctar ◽  
Jens Neugebauer ◽  
Thomas E. Schellin
Keyword(s):  
High Speed ◽  
Water Entry ◽  
The Other ◽  
Experimental Investigations ◽  
Air Trapping ◽  
Flat Bottom ◽  
Elastic Bottom ◽  
Bottom Structures ◽  
Two Bodies

Extensive water entry experiments were performed to identify the influence of elasticity on impact-induced loads acting of flat bottom structures. Two bodies were tested. One body was fitted with stiffened, rigid bottom plating; the other body, with thin elastic plating. Bottom pressures and forces acting on the flat bottom plating and impact-induced elastic bottom strains were measured. High-speed videos of water entry sequences were evaluated to investigate hydroelastic effects on air trapping.

scholarly journals Experimental evaluation of the air trapped during the water entry of flexible structures

ACTA IMEKO ◽  
2014 ◽  
Vol 3 (3) ◽  
pp. 63 ◽  
Author(s):  
Riccardo Panciroli ◽  
Giangiacomo Minak
Keyword(s):  
Flexible Structures ◽  
Processing Technique ◽  
Water Entry ◽  
Structural Deformation ◽  
Air Trapping ◽  
Flat Bottom ◽  
Initial Stage ◽  
Entry Velocity ◽  
Bottom Structures ◽  
The Impact

Deformable structures entering the water might experience several fluid-structure interaction (FSI) phenomena; air trapping is one of these. According to its definition, it consists of air bubbles trapped between the structure and the fluid during the initial stage of the impact. These bubbles might reduce the peak impact force. This phenomenon is characteristic for the water entry of flat-bottom structures. Above a deadrise angle of 10°, air trapping is negligible. In this work, we propose a methodology to evaluate the amount of air trapped in the fluid during the water entry. Experiments are performed on wedges with varying stiffness, entry velocity, and deadrise angle. A digital image post- processing technique is developed and utilized to track the air trapping mechanism and its evolution in time. Interesting results are found on the effect of the impact velocity and the structural deformation on the amount of air trapped during the slamming event.

scholarly journals Analysis of ATO System Operation Scenarios Based on UPPAAL and the Operational Design Domain

Electronics ◽  
2021 ◽  
Vol 10 (4) ◽  
pp. 503
Author(s):  
Zicong Meng ◽  
Tao Tang ◽  
Guodong Wei ◽  
Lei Yuan
Keyword(s):  
High Speed ◽  
Test Case ◽  
Design Domain ◽  
System Operation ◽  
High Speed Railway ◽  
Functional Specification ◽  
Operational Design ◽  
Train Operation ◽  
System Requirements ◽  
Automatic Train Operation

With the gradual maturity of the automatic train operation (ATO) system in subways, its application scope has also expanded to the high-speed railway field. Considering that the ATO system is still in the early stages of operation, it will take time to fully mature, and definite specifications of the requirements for system operation have not yet been formed. This paper presents the operational design domain (ODD) of the high-speed railway ATO system and proposes a scenario analysis method based on the operational design domain to obtain the input conditions of the system requirements. The article models and verifies the scenario of the linkage control of the door and platform door based on the UPPAAL tools and extracts the input and expected output of the system requirements of the vehicle ATO system. Combined with the input conditions of the system requirements, the system requirements of the vehicle ATO in this scenario are finally obtained, which provides a reference for future functional specification generation and test case generation.

Turbine Nozzle Endwall Phantom Cooling With Compound Angled Pressure Side Injection

2018 ◽  
Author(s):  
Kevin Liu ◽  
Hongzhou Xu ◽  
Michael Fox
Keyword(s):  
Film Cooling ◽  
High Speed ◽  
Axial Direction ◽  
Secondary Flows ◽  
Test Case ◽  
Pressure Side ◽  
Complex Flow ◽  
Trailing Edge ◽  
Cooling Effectiveness ◽  
Extended Area

Cooling of the turbine nozzle endwall is challenging due to its complex flow field involving strong secondary flows. Increasingly-effective cooling schemes are required to meet the higher turbine inlet temperatures required by today’s gas turbine applications. Therefore, in order to cool the endwall surface near the pressure side of the airfoil and the trailing edge extended area, the spent cooling air from the airfoil film cooling and pressure side discharge slots, referred to as “phantom cooling” is utilized. This paper studies the effect of compound angled pressure side injection on nozzle endwall surface. The measurements were conducted in a high speed linear cascade, which consists of three nozzle vanes and four flow passages. Two nozzle test models with a similar film cooling design were investigated, one with an axial pressure side film cooling row and trailing edge slots; the other with the same cooling features but with compound angled injection, aiming at the test endwall. Phantom cooling effectiveness on the endwall was measured using a Pressure Sensitive Paint (PSP) technique through the mass transfer analogy. Two-dimensional phantom cooling effectiveness distributions on the endwall surface are presented for four MFR (Mass Flow Ratio) values in each test case. Then the phantom cooling effectiveness distributions are pitchwise-averaged along the axial direction and comparisons were made to show the effect of the compound angled injection. The results indicated that the endwall phantom cooling effectiveness increases with the MFR significantly. A compound angle of the pressure side slots also enhanced the endwall phantom cooling significantly. For combined injections, the phantom cooling effectiveness is much higher than the pressure side slots injection only in the endwall downstream extended area.

Impact Flash at High Speed Water Entry

1951 ◽  
Vol 22 (3) ◽  
pp. 360-361 ◽  
Author(s):  
J. H. McMillen ◽  
R. L. Kramer ◽  
D. E. Allmand
Keyword(s):  
High Speed ◽  
Water Entry ◽  
Impact Flash

Supersonic Bi-Directional Flying Wing Wave Drag Optimization Based on Alternative Form of CST Method

2013 ◽  
Vol 477-478 ◽  
pp. 240-245
Author(s):  
Xiaohui Guan
Keyword(s):  
Drag Reduction ◽  
High Speed ◽  
Wave Drag ◽  
Alternative Form ◽  
Shape Transformation ◽  
Flat Bottom ◽  
Symmetric Configuration ◽  
Shape Parameterization ◽  
Wave Drag Reduction ◽  
Sufficient Precision

Bi-directional Flying Wing (BFW) is a new supersonic civil transport shape concept that aims to meet the conflict requirements of high speed cruise and low speed take-off/landing missions. In this paper the Class-Shape-Transformation (CST) shape parameterization method is modified to represent the BFW shape, and new basis functions suitable for the BFW airfoil representation are constructed. The Far-field Composite Element (FCE) wave drag optimization is performed on both the flat bottom and symmetric BFW configurations, and the drag reduction effects and result precision are surveyed. It is suggested that significant wave drag reduction can be achieved by the FCE optimization for both the flat bottom and the symmetric BFW configurations. The wave drag coefficients with sufficient precision can be obtained in the FCE optimization of the symmetric configuration; while the FCE optimization results of the flat bottom one are not accurate enough.

scholarly journals Reverse Thrust Aerodynamics of Variable Pitch Fans

2018 ◽  
Author(s):  
Tim S. Williams ◽  
Cesare A. Hall
Keyword(s):  
High Speed ◽  
Pressure Ratio ◽  
Test Case ◽  
Suction Surface ◽  
Flow Angle ◽  
Variable Pitch ◽  
Open Rotor ◽  
Weight Penalty ◽  
Reverse Thrust ◽  
Rotor Loss

Variable pitch fans are of interest for future low pressure ratio fan systems since they provide improved operability relative to fixed pitch fans. If they can also be re-pitched such that they generate sufficient reverse thrust they could eliminate the engine drag and weight penalty associated with bypass duct thrust reversers. This paper sets out to understand the details of the 3D fan stage flow field in reverse thrust operation. The study uses the Advanced Ducted Propulsor variable pitch fan test case, which has a design fan pressure ratio of 1.29. Comparison with spanwise probe measurements show that the computational approach is valid for examining the variation of loss and work in the rotor in forward thrust. The method is then extended to a reverse thrust configuration using an extended domain and appropriate boundary conditions. Computations, run at two rotor stagger settings, show that the spanwise variation in relative flow angle onto the rotor aligns poorly to the rotor inlet metal angle. This leads to two dominant rotor loss sources: one at the tip associated with positive incidence, and the second caused by negative incidence at lower span fractions. The second loss is reduced by opening the rotor stagger setting, and the first increases with rotor suction surface Mach number. The higher mass flow at more open rotor settings provide higher gross thrust, up to 49% of the forward take-off value, but is limited by the increased loss at high speed.

COMPARISON OF UNSTEADY REYNOLDS-AVERAGED NAVIER-STOKES PREDICTION OF SELF-PROPELLED CONTAINER SHIP SQUAT AGAINST EMPIRICAL METHODS AND BENCHMARK DATA

2021 ◽  
Vol 162 (A2) ◽  
Author(s):  
Z Kok ◽  
J T Duffy ◽  
S Chai ◽  
Y Jin
Keyword(s):  
Water Depth ◽  
High Speed ◽  
Navier Stokes ◽  
Container Ship ◽  
Benchmark Data ◽  
High Speeds ◽  
Port Throughput ◽  
Finite Water Depth ◽  
Urans Cfd ◽  
Effective Wake

The demand to increase port throughput has driven container ships to travel relatively fast in shallow water whilst avoiding grounding and hence, there is need for more accurate high-speed squat predictions. A study has been undertaken to determine the most suitable method to predict container ship squat when travelling at relatively high speeds (Frh ≥ 0.5) in finite water depth (1.1 ≤ h/T ≤ 1.3). The accuracy of two novel self-propelled URANS CFD squat model are compared with that of readily available empirical squat prediction formulae. Comparison of the CFD and empirical predictions with benchmark data demonstrates that for very low water depth (h/T < 1.14) and when Frh < 0.46; Barass II (1979), ICORELS (1980), and Millward’s (1992) formulae have the best correlation with benchmark data for all cases investigated. However, at relatively high speeds (Frh ≥ 0.5) which is achievable in deeper waters (h/T ≥ 1.14), most of the empirical formulae severely underestimated squat (7-49%) whereas the quasi-static CFD model presented has the best correlation. The changes in wave patterns and effective wake fraction with respect to h/T are also presented.

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