Thermoplastic composite pipes (TCPs) are increasingly used to transport hydrocarbons and water in the oil and gas industry due to their superior properties including corrosion resistance, thermal insulation, light weight, etc. The cross-section of TCPs generally consists of three layers: inner liner, composite laminate, and outer jacket. Three layers are bonded together and form a solid-wall construction. Inner liner and outer jacket made of thermoplastic polymer provide protective barriers for the laminate to against the inner fluid and outer environment. The laminate is constructed by an even number of helically wounded continuous fiber reinforced thermoplastic composite tapes. In this study, mechanical behaviors of a TCP under an internal pressure were investigated by using analytical and finite element analysis (FEA) methods. The analytical method which is based on the three-dimensional (3D) anisotropy elastic theory can take account of non-uniformly distributed stress and strain through the thickness of the pipe wall. FEA models were setup by using the software ABAQUS to predict the stress distribution of the pipe. 3D Tsai-Wu failure criterion was used to predict the maximum internal pressure of the pipe. Effects of some critical parameters, such as the winding angle of composite tapes and the number of reinforced plies, on the internal pressure capacity of TCPs were studied. Results obtained from the analytical and FEA methods were fairly agreed with each other, which showed that with the increasing of the number of reinforced plies the internal pressure capacity of a TCP gradually increases and approaches to an extreme value. In addition, the optimal winding angle which results the maximum internal pressure is not a constant value, instead, it varies with the increasing thickness of the laminate layer. This study provides useful tools and guidance for the design and analysis of TCPs, and is currently under validation through experiments.

Subsea pipelines are prone to be damaged by the falling objects from ships or offshore platforms, which may result in economic losses and pollution. The dimensions of dent were commonly used to evaluate the impact resistance of pipes made from carbon steel. Thermoplastic composite pipes (TCPs), due to their superior properties including corrosion resistance, thermal insulation, fast installation, etc., are increasingly used as the subsea pipelines. The TCP is made from thermoplastic resins and reinforced by continuous fibers. Because of the brittle nature of carbon fibers and glass fibers, the dimensions of dent are not suitable for assessment of impact resistance of a TCP. In the present work, a procedure was proposed using the internal pressure capacity as an indicator to evaluate the lateral impact resistance of a TCP. First, the internal pressure capacity of an intact TCP was evaluated. Second, a quasi-static simulation was conducted by applying a lateral compression force on the intact TCP using a rigid ball, until one of the composite plies in the reinforcement layer failed. The quasi-static simulation provided an initial estimate of the minimum energy that causes the start of damage of the TCP. Third, the impact simulations were performed by using a rigid ball hitting the TCP and, then, the internal pressure capacity of the damaged TCP was evaluated. Finally, the internal pressure capacity of the damaged pipe, compared with that of the intact pipe, was used as an indicator to evaluate the lateral impact resistance of the TCP. In this study, a glass-fiber reinforced polyethylene (PE) pipe of an inner diameter of 150 mm was modeled by ABAQUS to illustrate the procedure. A theoretical method was proposed to calculate the impact energy of a dropped object in a shallow water. The example studied in the present work showed that the modeled TCP was not strong enough to survive the lateral impact caused by the dropped object and should be buried to a certain depth beneath the seabed if used as a subsea pipeline.

A quantitative and time-resolved radiographic has been used to characterize direct-injection (Dl) gasoline sprays in near-nozzle region. The highly penetrative nature of x-rays promises the direct measurements of dense sprays that are difficult to study by visible-light optical techniques. Appropriate models were developed to determine the fuel volume fraction as a function of time and positions. The results also show quantitatively the strong asymmetry of the hollow-cone sprays studied here.

Flexible cylinders, such as marine risers, often experience sustained vortex-induced vibration (VIV). Both helical strakes and fairings are demonstrated to be effective in suppressing VIV, while, helical strakes result in large drag, which increases the rotational angle and bending moment at the riser hang-off location and, fairings are cumbersome in term of storage, installation and maintenance. This study was inspired by the giant Saguaro Cacti which grow in desert region. Saguaro Cacti have shallow root system, but can grow up to fifty feet in height and can withstand very high wind velocities. In this study, numerical simulations of flow past a stationary cactus-shaped cylinder are performed in two-dimensional field at a low Reynolds number of 200. The hydrodynamic coefficients and the vortex-shedding patterns of a cactus-shaped cylinder are compared with those of a circular cylinder. In addition, a set of two cactus-shaped cylinders of tandem arrangement are also studied to investigate the effects of wake. Results showed that a cactus-shaped cylinder can reduce the drag, lift, and Strouhal number, which suggests its potential as an alternative technology to suppress VIV of a riser.

Vortex-induced vibration (VIV) excited by current is a major contributor to the fatigue accumulation of marine risers. For deepwater operations, several risers are often arranged together in an array configuration. In this study, a set of four identical flexible pipes of a rectangular arrangement were tested in a water tunnel. By comparing the dynamic responses of a pipe in an array with that of a single isolated pipe, the effects of the current speed and the center-to-center distance between the up-stream and downstream pipes on their dynamic responses were investigated. Fatigue damages accumulated on each pipe in an array was calculated and a factor, termed “fatigue damage amplification factor”, was defined as a ratio between the fatigue damage rate of pipe in an array and the fatigue damage rate of a single pipe at a same current condition. The results showed that for bare pipes (i.e., without helical strakes), the downstream pipes in an array configuration may have larger dynamic responses and fatigue damage rates than those of a single pipe; and, it is not always conservative to assume that the fatigue damage rate estimated for a single pipe can be used to represent the fatigue damage rates of pipes in an array. This preliminary study provided some meaningful results for the design, analysis and operation of marine riser arrays.

Scanning beam interference lithography (SBIL) technology is applied to produce large-area grating with nanoscale phase accuracy. One of the greatest challenges of SBIL is locking interference fringe to a moving substrate with nanometer spatial phase error, which requires measuring the fringe phase with subnanometer precision. We are developing a novel homodyne phase-locking interferometer (HPLI) to meet the harsh measurement requirements. The HPLI offers high precision phase measurements as well as the direction recognition of the interference fringe drift with a four-orthogonal detection system. However, nonlinearity error impacts the phase measurement accuracy of HPLI with nanometer scale, which is mainly due to polarization mixing. In this paper, we present a method to estimate and compensate nonlinearity error in real time by applying an extended Kalman filter algorithm. The simulation results show that the method can effectively eliminate the nonlinearity error.

The solution accuracy and computational efficiency of high order Large Eddy Simulation (LES) solvers are evaluated on two benchmark open literature blade cascade problems. The first problem concerns wake development in the T106A low pressure turbine cascade [1]. The second problem examines the effect of free-stream turbulence on heat transfer from the VKI first stage high pressure turbine vane [2]. The calculations are performed with two independently developed high order LES solvers using completely different numerical algorithms. The first solver FDL3Di [3] was originally developed at the Airforce Research Laboratory (AFRL) and employs structured overset grids. It uses a sixth order compact finite difference scheme in space along with an implicit Beam-Warming scheme for time marching. The second solver, hpMusic, is developed at the University of Kansas [4]. This is a variable order (up to sixth order) unstructured grid solver employing a discontinuous formulation known as flux reconstruction (FR) / correction procedure via reconstruction (CPR) [5]. The computational grids used are independently tuned for each application. The solvers are benchmarked against experimental data for wake development and blade heat transfer coefficient. Further physical insights in to the test cases are also obtained, filling gaps in experimental results, especially for the VKI problem.

To analyze structural dynamic response of rotary ultrasonic motor under high impact load, a theoretical model is established in this paper. A rotary ultrasonic motor includes two main components: stator and rotor. According to structure form and movement principle, they can be simplified as annular plates. When the system is imparted an impact load, dynamic displacement response of stator and rotor can be obtained. The damage to stator and rotor is analyzed in theory. It gave agreement with simulation and experimental result. Finally, influence of various structure parameters on the deformation of stator and rotor is analyzed and some suggestions on improving performance of rotary type ultrasonic motor are proposed.

The Lanthanum-doped lead zirconate titannate (PLZT) ceramic can be able to drive a micro-mirror according to its excellent advantages such as less susceptible to electromagnetic interference, non-contact optical control and other features. However, the slow response of the photo-deformation and inherent hysteresis extremely limit its wide applications, especially in the dynamic fields of high frequency. To solve above-mentioned problems, this paper proposes an optical-electrostatic driving approach to actuate a device including two parallel electrode plates and a micro-mirror. For the experiment, the SMF-28 fiber with a diameter of 8.2um was selected and the displacement and photovoltage of the PLZT ceramic when irradiated with ultraviolet light of 200mWcm −2 were measured and analyzed. The results show that the response time of the PLZT ceramic obtains 20s when the deformation displacement reaches over 8.2um. Based on the proposed hybrid optical-electrostatic driving device, the deformation displacement is demonstrated to be 9.17um by applying 300V voltage to the parallel electrode plates. Furthermore, the response time reduces to almost 1s when the photovoltage of PLZT is applied with 300V, which indicates that the proposed hybrid optical-electrostatic driving mechanism can significantly eliminate the effect of slow response of photo-deformation.

It is experimentally confirmed that the response speed of photo-induced deformation lags far behind the photovoltage and it is difficult to control the magnitude of the photo-induced electric field in PLZT ceramic due to the serious residual photovoltage. The primary purpose of this article is to control the photovoltage of PLZT for a photovoltaic-electrostatic driven servo system proposed in this paper. The control equations of photovoltage for photovoltaic-electrostatic driven servo system are derived based on the mathematical model of PLZT with coupled multi-physics fields. Parameters of photovoltage of PLZT ceramic during the illumination phase and light off phase are identified through the static experiment. Based on simple on-off control strategy, real-time switching the UV light via an optical shutter is adopted to achieve the desired photovoltage. Then, the closed-loop photovoltage control experiments for photovoltaic-electrostatic driven servo system based on PLZT ceramic are carried out. The experimental results show that the photovoltage can be successfully controlled at the target degree by switching the UV light with an optical shutter. The control strategy can be applied in the photovoltaic-electrostatic driven servo system to achieve the target degree of angular or displacement deflection.

When ultraviolet light illuminates on polarized PLZT ceramic, a large voltage can be generated between the electrodes due to the anomalous photovoltaic effect. The shape control of flexible shell can be realized by using hybrid photovoltaic/piezoelectric actuation. In this paper, a novel non-contact deflection closed-loop control model of cantilever beam based on hybrid photovoltaic/piezoelectric actuation can be proposed. The photovoltage of PLZT ceramic irradiated by ultraviolet light is applied to drive PVDF actuator. The closed-loop control equations of deflection of cantilever beam is derived based on the mathematical model of PLZT ceramic with coupled multi-physics fields and the constitutive model of cantilever beam. Then, parameters of deflection control equations of cantilever beam during illumination phase and light off phase are identified through the deflection static experiment. After that, the deflection closed-loop control experiment of cantilever beam based on hybrid photovoltaic/piezoelectric actuation mechanism is carried out to verify the control model. The experimental results show that the deflection of cantilever beam with a simple on-off control method can achieve the target value by applying UV light to PLZT ceramic. It also should be noted that, the deflection curve of cantilever beam illuminated by strong UV light has an undesirable fluctuation.