Broad-band geoacoustic inversion in shallow water from waveguide impulse response measurements on a single hydrophone: theory and experimental results

One of the phenomena restricting the tanker navigation in shallow waters is reduction of under keel clearance in the terms of sinkage and dynamic trim that is called squatting. According to the complexity of flow around ship hull, one of the best methods to predict the ship squat is experimental approach based on model tests in the towing tank. In this study model tests for tanker ship model had been held in the towing tank and squat of the model are measured and analyzed. Based on experimental results suitable formulae for prediction of these types of ship squat in fairways are obtained.

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Rotordynamics Performance of Hybrid Foil Bearing Under Forced Vibration Input

Volume 7A: Structures and Dynamics ◽

10.1115/gt2017-65233 ◽

2017 ◽

Author(s):

Daejong Kim ◽

Brian Nicholson ◽

Lewis Rosado ◽

Garry Givan

Keyword(s):

Impulse Response ◽

High Speed ◽

Load Capacity ◽

Supply System ◽

Forced Response ◽

Experimental Results ◽

Lateral Acceleration ◽

Foil Bearings ◽

Foil Bearing ◽

Gas Supply

Foil bearings are one type of hydrodynamic air/gas bearings but with a compliant bearing surface supported by structural material that provides stiffness and damping to the bearing. The hybrid foil bearing (HFB) in this paper is a combination of a traditional hydrodynamic foil bearing with externally-pressurized air/gas supply system to enhance load capacity during the start and to improve thermal stability of the bearing. The HFB is more suitable for relatively large and heavy rotors where rotor weight is comparable to the load capacity of the bearing at full speed and extra air/gas supply system is not a major added cost. With 4,448N∼22,240N thrust class turbine aircraft engines in mind, the test rotor is supported by HFB in one end and duplex rolling element bearings in the other end. This paper presents experimental work on HFB with diameter of 102mm performed at the US Air force Research Laboratory. Experimental works include: measurement of impulse response of the bearing to the external load corresponding to rotor’s lateral acceleration of 5.55g, forced response to external subsynchronous excitation, and high speed imbalance response. A non-linear rotordynamic simulation model was also applied to predict the impulse response and forced subsynchronous response. The simulation results agree well with experimental results. Based on the experimental results and subsequent simulations, an improved HFB design is also suggested for higher impulse load capability up to 10g and rotordynamics stability up to 30,000rpm under subsynchronous excitation.

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Tubuloglomerular feedback dynamics and renal blood flow autoregulation in rats

AJP Renal Physiology ◽

10.1152/ajprenal.1991.260.1.f53 ◽

1991 ◽

Vol 260 (1) ◽

pp. F53-F68 ◽

Cited By ~ 40

Author(s):

N. H. Holstein-Rathlou ◽

A. J. Wagner ◽

D. J. Marsh

Keyword(s):

Blood Flow ◽

Arterial Pressure ◽

Renal Blood Flow ◽

Slow Component ◽

Broad Band ◽

Experimental Results ◽

Tubuloglomerular Feedback ◽

Single Frequency ◽

Vascular Control ◽

Arterial Blood

To decide whether tubuloglomerular feedback (TGF) can account for renal autoregulation, we tested predictions of a TGF simulation. Broad-band and single-frequency perturbations were applied to arterial pressure; arterial blood pressure, renal blood flow and proximal tubule pressure were measured. Data were analyzed by linear systems analysis. Broad-band forcings of arterial pressure were also applied to the model to compare experimental results with simulations. With arterial pressure as the input and tubular pressure, renal blood flow, or renal vascular resistance as outputs, the model correctly predicted gain and phase only in the low-frequency range. Experimental results revealed a second component of vascular control active at 100-150 mHz that was not predicted by the simulation. Forcings at single frequencies showed that the system behaves linearly except in the band of 33-50 mHz in which, in addition, there are autonomous oscillations in TGF. Higher amplitude forcings in this band were attenuated by autoregulatory mechanisms, but low-amplitude forcings entrained the autonomous oscillations and provoked amplified oscillations in blood flow, showing an effect of TGF on whole kidney blood flow. We conclude that two components can be detected in the dynamic regulation of renal blood flow, i.e., a slow component that represents TGF and a faster component that most likely represents an intrinsic vascular myogenic mechanism.

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Determination of Stability Derivatives by Impulse-Response Techniques

Marine Technology and SNAME News ◽

10.5957/mt1.1977.14.2.265 ◽

1977 ◽

Vol 14 (02) ◽

pp. 265-275

Author(s):

Carl A. Scragg

Keyword(s):

Memory Effect ◽

Impulse Response ◽

Traditional Method ◽

Equations Of Motion ◽

Experimental Results ◽

Regular Motion ◽

Stability Derivatives ◽

The Stability ◽

Derivatives Of

This paper presents a new method of experimentally determining the stability derivatives of a ship. Using a linearized set of the equations of motion which allows for the presence of a memory effect, the response of the ship to impulsive motions is examined. This new technique is compared with the traditional method of regular-motion tests and experimental results are presented for both methods.

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Nonlinear Fourier Analysis for Shallow Water Waves

10.1115/omae2021-63933 ◽

2021 ◽

Author(s):

Alfred R. Osborne

Keyword(s):

Fourier Series ◽

Fourier Analysis ◽

Shallow Water ◽

Nonlinear Wave ◽

Water Waves ◽

Wave Equations ◽

Superposition Principle ◽

Broad Band ◽

Kp Equation ◽

Linear Superposition

Abstract I consider nonlinear wave motion in shallow water as governed by the KP equation plus perturbations. I have previously shown that broad band, multiply periodic solutions of the KP equation are governed by quasiperiodic Fourier series [Osborne, OMAE 2020]. In the present paper I give a new procedure for extending this analysis to the KP equation plus shallow water Hamiltonian perturbations. We therefore have the remarkable result that a complex class of nonlinear shallow water wave equations has solutions governed by quasiperiodic Fourier series that are a linear superposition of sine waves. Such a formulation is important because it was previously thought that solving nonlinear wave equations by a linear superposition principle was impossible. The construction of these linear superpositions in shallow water in an engineering context is the goal of this paper. Furthermore, I address the nonlinear Fourier analysis of experimental data described by shallow water physics. The wave fields dealt with here are fully two-dimensional and essentially consist of the linear superposition of generalized cnoidal waves, which nonlinearly interact with one another. This includes the class of soliton solutions and their associated Mach stems, both of which are important for engineering applications. The newly discovered phenomenon of “fossil breathers” is also characterized in the formulation. I also discuss the exact construction of Morison equation forces on cylindrical piles in terms of quasiperiodic Fourier series.

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