https://pure.hw.ac.uk/ws/files/34728103/ECM_2020_hybrid_VIV_gallop.pdf

Hybrid wind energy scavenging by coupling vortex-induced vibrations and galloping

We have demonstrated the effectiveness of reinforcement learning (RL) in bluff body flow control problems both in experiments and simulations by automatically discovering active control strategies for drag reduction in turbulent flow. Specifically, we aimed to maximize the power gain efficiency by properly selecting the rotational speed of two small cylinders, located parallel to and downstream of the main cylinder. By properly defining rewards and designing noise reduction techniques, and after an automatic sequence of tens of towing experiments, the RL agent was shown to discover a control strategy that is comparable to the optimal strategy found through lengthy systematically planned control experiments. Subsequently, these results were verified by simulations that enabled us to gain insight into the physical mechanisms of the drag reduction process. While RL has been used effectively previously in idealized computer flow simulation studies, this study demonstrates its effectiveness in experimental fluid mechanics and verifies it by simulations, potentially paving the way for efficient exploration of additional active flow control strategies in other complex fluid mechanics applications.

https://www.pnas.org/content/pnas/117/42/26091.full.pdf

Reinforcement learning for bluff body active flow control in experiments and simulations.

A hybrid piezo-dielectric wind energy harvester for high-performance vortex-induced vibration energy harvesting

As a fundamental fluid-structure interaction (FSI) phenomenon, vortex-induced vibrations (VIVs) of circular cylinders have been the center of the FSI research in the past several decades. Apart from its scientific significance in rich physics, VIVs are paid great attentions by offshore engineers, as they are encountered in many ocean engineering applications. Recently, with the development of research and application, wake-induced vibration (WIV) for multiple cylinders and galloping for VIV suppression attachments are attracting a growing research interest. All these phenomena are connected with the flow-induced vibration (FIV). In this paper, we review and give some discussions on the FIV of offshore circular cylinders, including the research progress on the basic VIV mechanism of an isolated rigid or flexible cylinder, interference of multiple cylinders concerning WIV of multiple cylinders, practical VIV suppression and unwanted galloping for cylinder of attachments. Finally, we draw concluding remarks, give some comments and propose future research prospects, especially on the major challenges as well as potentials in the offline/online modelling and prediction of real-scale offshore structures with high-fidelity CFD methods, new experimental facilities and applications of artificial intelligence tools.

A review on flow-induced vibration of offshore circular cylinders

Control of vortex-induced vibration of a circular cylinder using a pair of air jets at low Reynolds number

Simultaneous CFD evaluation of VIV suppression using smaller control cylinders

The invention relates to an experimental device and method for simulating wellbore annulus drilling fluid flow characteristics. The method includes the steps of simulating an wellbore annulus through an outer cylinder and a simulating drill rod and fixing the wellbore annulus on a supporting platen, driving the simulating drill rod to rotate through a rotating motor, controlling the rotating speed of the simulating drill rod, injecting mud into the wellbore annulus between the outer cylinder and the simulating drill rod through a mud pump, controlling the flow of the mud, controlling a lifting motor to adjust the angle between the supporting platen and the horizontal line, and controlling the drill rod eccentricity through a specially-made eccentric hole flange plate. According to the experimental device and method, the wellbore annulus drilling fluid flow characteristics can be simulated under different drill rod rotating speeds, different types of flow, different hole drift angles and different eccentric distances, requirements of different working conditions are met, the mud used for experiments can be repeatedly pumped into the wellbore annulus and recycled, and cost is saved.

Experimental device and method for simulating wellbore annulus drilling fluid flow characteristics

The utility model relates to a device for hindering vortex-induced vibration of trepanning and diverting spiral strakes. The device for hindering vortex-induced vibration of the trepanning and diverting spiral strakes is formed by combining multiple basic units in the direction of an ocean vertical tube axis in series. Each basic unit is composed of a sleeve and the spiral strake provided with diverting holes and is machined and formed at a time by a plastic mold. The sleeves are coaxial with vertical tubes and the sleeves are directly and fixedly arranged on the vertical tubes in a sleeved mode. Three spiral strakes are arranged on the outer surfaces of the sleeves and evenly distributed in 120 degrees. Each spiral strake rotates around the corresponding sleeve by one loop. Four diverting holes are formed in each spiral strake in the vertical tube axis direction at equal vertical height intervals. According to the device for hindering vortex-induced vibration of the trepanning and diverting spiral strakes, the sleeves of the trepanning and diverting spiral strakes are arranged outside the vertical tubes in a sleeved mode in series, thus vortex-induced vibration caused by currents from different directions can be hindered effectively, the influences on the fatigue life of the vertical tubes are reduced, and the device is light in weight, low in manufacturing cost, and not prone to abrasion or damage.

Device for hindering vortex-induced vibration of trepanning and diverting spiral strakes

The utility model relates to a riser vortex inducting vibration suppression device with a rough undulating surface The riser vortex inducting vibration suppression device with the rough undulating surface is formed by combining a plurality of elementary units in series along the axis direction of a marine riser, wherein each elementary unit is composed of two semi-symmetric plastic undulating semicircular cylinders, each undulating semicircular cylinder is of solid structure, the outer surface of each undulating semicircular cylinder is in rolling wave shape, and semi-ellipsoid bulges and semi-ellipsoid pits are evenly distributed along the circumferential direction of the wave crest and the wave trough of the wave-shaped outer surface of each undulating semicircular cylinder According to the riser vortex inducting vibration suppression device with the rough undulating surface, the wave-shaped surface of the riser vortex inducting vibration suppression device enables streaming to be in three-dimensional mixing mode, flow fields close to the wall of the riser vortex-induced vibration suppression device is perturbed due to the fact that the surface of the riser vortex-induced vibration suppression device is rough, formation and development of vortexes are effectively suppressed under the influence of the rough undulating surface of the riser vortex-induced vibration suppression device, and accordingly vortex inducting vibration suppression is achieved The riser vortex inducting vibration suppression device with the rough undulating surface can deal with incoming flows from different directions, is low in cost and difficult to corrode and damage, and can be reused

Riser vortex inducting vibration suppression device with rough undulating surface

The invention relates to a device and a method for inhibiting vortex-induced vibration of a spiral strake with rotating blades. The device for inhibiting vortex-induced vibration of the spiral strake with the rotating blades is characterized by being combined by multiple basic units, and each basic unit is composed of a sleeve, spiral strakes and blades; three spiral strakes are arranged on the outer surface of the sleeve and are uniformly distributed in 120 degrees, each spiral strake rotates around the sleeve for one circle, and six blades which can rotate freely are mounted on three vertical lines in the circumferential direction of the outer side of the sleeve; under the action of ocean current, the blades are driven to rotate, and a streaming boundary layer of a vertical pipe is destroyed; under the combined action of the spiral strakes and the blades, a streaming flow field of the vertical pipe is fundamentally destroyed, so that a vortex-induced vibration inhibiting effect is improved. The device for inhibiting vortex-induced vibration of the spiral strake with the rotating blades is processed by plastic, low in cost and resistant to corrosion and can be repeatedly used.

Ma Yue

Papers

Simultaneous CFD evaluation of VIV suppression using smaller control cylinders

Experimental device and method for simulating wellbore annulus drilling fluid flow characteristics

Device for hindering vortex-induced vibration of trepanning and diverting spiral strakes

Riser vortex inducting vibration suppression device with rough undulating surface

Device and method for inhibiting vortex-induced vibration of spiral strake with rotating blade