Spiral Flow Research Articles

Exergy loss analysis on heat transfer characteristics of twisted petaloid spirally wound tube with the convection boundary condition

• 1. Heat transfer characteristics of the twisted petaloid spiral wound tube (TPSWT) are investigated. • 2. Expression of heat transfer exergy loss number (HTELN) is derived. • 3. Characteristics of the HTELN is studied. • 4. Correlation of the HTELN for the TPSWT is formulated. The spiral flow motivates an extra centrifugal force inducing the secondary flow to effectively enhance the heat transfer performance of spirally wound tubes (SWTs). In this research, the flow and heat transfer characteristics of twisted petaloid spirally wound tube (TPSWT) basis of exergy theory was numerically analyzed, which integrates the technologies of spiral coil, petaloid section and twisted channel. Firstly, the flow and heat transfer characteristics of the TPSWT are numerically investigated. Secondly, the heat transfer exergy loss number (HTELN, ζ HT ) is proposed. Furthermore, the relationship between η (heat transfer effectiveness) and ζ HT is investigated. Finally, the correlations for Nu petal , η and ζ HT in the form of classical power–law expression are calculated. The results show that, the secondary flow induced by the integration of the centrifugal force and the torsional force destroying the steady flow state, which enhances the heat transfer performance; ζ HT can describe the heat transfer performance in 2 aspects, one is for the heat transfer irreversible loss, the other one is for the heat transfer efficiency; the predicted values of the regression functions are well aligned with the numerical calculated data (6.73% for Nu petal ; 1.68% for η; 0.38% for ζ HT ).

Numerical Analysis of the Erosion Mechanism inside the Tube Sockets of Main Steam Thermometers in a Coal-Fired Power Plant

Leakage occurring in the tube sockets of the main steam thermometers can seriously threaten the safe operation of coal-fired power plants. Here, assuming a 300 MW unit as a relevant testbed, this problem is investigated numerically through solution of the equations of fluid-dynamics in synergy with the mathematical treatment of relevant statistics. The results indicate that the steam can form a large-scale spiral flow inside the tube socket and continuously scour the inner wall. In the model with the protective casing setting angle of 60°, the average tangential fluid velocity can reach up to 4.8 m/s, which is about twice higher than that in the model with the protective casing setting angle of 0°. The wake disturbance generated by the flow around the thermo-sensitive body leads to differences in the fluid motion inside the tube sockets between the upstream and downstream thermometers. These differences are affected by the distance between the thermometers, the setting angle of protective casing, and other factors. The pressure of the main steam inside the tube socket for a R3 thermometer, located outside the curved pipeline, is about 1756 Pa higher than that of the L3 thermometer located outside the straight pipeline, indicating that the secondary flow generated in the curved pipeline is able to provide stronger energy for the large-scale spiral flow inside the tube socket. On the basis of these findings, an improvement scheme for the installation of longitudinal ribs in the tube sockets is proposed. The simulation results show that the average tangential velocity of the fluid within the near-wall area of tube sockets decreases by more than 90%, which should be enough to effectively alleviate the damage to the inner wall caused by high-pressure fluid or particles.

Experimental studies and 3D simulations for the investigation of thermal performances of a solar air heater with different spiral-shaped baffles heights

A new design of Solar Air Heater (SAH) with spiral flow path is studied experimentally and numerically. The spiral-shaped SAH performance is studied at various mass flow rates, inlet temperatures, radiation intensity and baffle heights. Similarly, a CFD model is developed using “ANSYS Fluent” software to study the fluid flow and heat transfer in the SAH. Mesh independence is performed in order to choose the appropriate mesh. The discrete ordinate (DO) radiation model and the k-ω Shear Stress Transport (SST) turbulence model are used to study the radiative heat transfer and the turbulent flow, respectively in the SAH. Effects of different baffle heights (42 mm,50 mm,70 mm,90 mm, 110 mm and 130 mm) for different mass flow rates (input velocities:5 m/s,10 m/s,15 m/s, 20 m/s and 25 m/s) are numerically investigated. Local flow characteristics are presented and discussed. The results show a good agreement between the numerical model and the experimental data with an average error of 3.6%. The maximum outlet air temperature of the SAH during the test days reached 77.7 °C with input velocity of 5 m/s. The maximum thermal efficiency is founded for geometries having 110 mm and 130 mm baffle-heights ranges between 40% and 59% for an airflow of 0.0075 kg/s and 0.038 kg/s, respectively. The geometry having a 110 mm baffle-heights shows the optimum thermal performance of 13% higher than standard geometry (50 mm baffle height).

MRI visualization of aortic recoarctation in the long-term period after surgery (case report)

Case study. Aortic coarctation refers to well-known and well-studied congenital malformations of the cardiovascular system. The success of cardiovascular surgery significantly increased the survival rate of patients, but, unfortunately, did not reduce the risks of serious cardiovascular complications in the long-term postoperative period. One of the significant complications remains recoarctation – repeated narrowing in the area of surgery, which can initiate other complications.The purpose of the study: to present the features of blood flow in the aorta in a patient with aortic coarctation in the long-term postoperative period on the clinical example of a complex MR examination.Material and methods. A 12-year-old patient, at the age of 6, she underwent balloon angioplasty of aortic coarctation. Echocardiographic data revealed a residual gradient at the isthmus of the aorta and expansion of the descending aorta. To clarify the diagnosis, MRI angiography of the heart was performed with intravenous contrast and the use of a cardiopackage for 4D flow analysis (4D flow).Results and discussion. According to the MRI study, a narrowing of the distal aortic arch with aortic dilation after the departure of the left subclavian artery was revealed, which is confirmed by the obtained absolute values of blood flow indicators. MR-angiography of the aortic arch made it possible to visually determine the “gothic” shape of the aortic arch and present 3D reconstructions. 4D flow maps showed acceleration of blood flow to the systole in the area of aortic narrowing, additional vortex flow below the area of aortic narrowing and spiral flow in the descending aorta, which persisted throughout the diastole.One explanation for the abnormal spiral flow in the descending thoracic aorta may be the presence of a “gothic” aortic arch. Also, residual hypoplasia of the aortic arch and narrowing of the isthmus are the leading parameters affecting the pathophysiology of changes in blood pressure during exercise.Conclusion. The 4D-flow MR package in vivo makes it possible to study the flow geometry and blood flow parameters in detail, to obtain a detailed picture of the aortic condition, which gives potential advantages in a comprehensive examination of patients with aortic coarctation under dynamic observation.

Study of the Internal Cyclonic Flow Characteristics of Cyclones with Different Guide Vane Heights

To investigate the influence of the guide vane height on the cyclonic flow characteristics of guide vane cyclones, this paper mainly adopts a combination of numerical simulation and physical experiments, taking the guide vane height as the research object, analysing the internal spiral flow generation law through the flow velocity distribution in each section of the cyclone and the change trend along the course and comparing the tangential velocity, radial velocity and axial velocity characteristics of the cyclone at different guide vane heights. The results show that the tangential velocity increases with the increase in the guide vane height on the cyclone and then decreases. When the ratio between the height of the guide vane and the inner radius of the cyclone is in the range of 0.5–0.7, a higher−strength and more stable spiral flow can be produced, and the tangential velocity reaches the maximum when the guide vane height is 30 mm and the height−to−diameter ratio is around 0.6. As the height of the guide vane increases, the radial velocity area towards the wall of the tube increases, while the radial velocity area towards the tube axis decreases. The overall distribution of axial flow velocity is similar to that of turbulent flow in a circular tube, and the velocity increases with increasing height of the guide vane. The conclusion of this paper provides a theoretical basis for further optimisation of the cyclone structure parameters.

Endometrial microstimulation effects on endometrial receptivity assessed by transvaginal color Doppler sonography.

This study investigated the effect of endometrial microstimulation (EM) on endometrial receptivity using transvaginal color Doppler sonography (TVCDS). Women of childbearing age who were preparing to conceive (n = 90) were randomly divided into the EM group (n = 30), who were examined by EM on days 3-5 of the menstrual cycle, and the control group (n = 60). TVCDS was conducted during the implantation window phase, and endometrial thickness, endometrial pattern, endometrial movement, blood flow type, and uterine and spiral arterial hemodynamic parameter measurements were made. The groups were compared to identify differences. Endometrial thickness (0.97 ± 0.18cm and 0.95 ± 0.17cm), endometrial movement (type 1: 46.7% and 51.7%; type 2: 30.0% and 28.3%; type 3: 6.7% and 5.0%; type 5: 16.7% and 15.0%), and hemodynamic parameters of the uterine (pulsatility index [PI]: 2.46 ± 0.50 and 2.41 ± 0.48; resistance index [RI]: 0.85 ± 0.05 and 0.84 ± 0.05) and spiral (PI: 1.11 ± 0.32 and 1.19 ± 0.33; RI: 0.48 ± 0.11 and 0.51 ± 0.08) arteries did not differ significantly between groups (P > 0.05). However, the endometrial pattern (a trilaminar pattern: 80.0% and 58.3%; P = 0.041) and blood flow type (type I: 16.7% and 43.3%; type II: 63.3% and 40.0%; type III 20.0% and 16.7%; P = 0.038) differed significantly between groups. Endometrial microstimulation did not alter endometrial pathological staging, endometrial thickness, or movement, nor did it affect uterine and spiral arterial blood flow parameters. However, it may be able to abrade abnormal endometrial tissue, optimizing the endometrial pattern. Endometrial microstimulation may support local spiral artery regeneration and increase endometrial blood supply in new cycles.

Magnetohydrodynamic Energy Harvester for Low-Power Pipe Instrumentation

Smart pipes can be adopted as a solution to problems in water distribution systems. However, the real application of such a system is usually constrained by power delivery. In this article, a magnetohydrodynamic (MHD) energy harvester for low-power pipe instrumentation is developed. A theoretical model of the maximum power output containing parameters of water conductivity, flow velocity, magnetic flux density, and water channel volume is derived. To enhance the magnetic flux density, a magnetic concentrator is designed and carefully tuned to arrange the magnetic flux as we desire and magnify the magnetic flux density within the channels. A spiral flow diverter is proposed to reconfigure the original pipe flow pattern and divert the flow into the surrounding channels to enhance the flow velocity. After integrating the proposed improvements from different fields and globally optimizing the power output, a final design is prototyped and tested in the lab, which achieves a maximum power output of 87.47 nW with a 2-m/s pipe inlet velocity. To the best of our knowledge, this is the first MHD energy harvester for low-power sensor networks. Its great potential is demonstrated, and several potential enhancements to the power output are proposed and analyzed.

The special solutions of 2-D steady isentropic irrotational relativistic Euler system

In this paper, we study the special solutions of the steady isentropic irrotational relativistic Euler system with perfect gas. We convert this system into a series of two-order linear PDEs and then obtain three kinds of special solutions. These solutions correspond to the circulatory flow, the radial flow, and the spiral flow, respectively.

Numerical analysis of propulsion performance of a waterjet-propelled vehicle in steady drift

This paper analyzes the propulsion performance and the correlating flow details of a waterjet–propelled vehicle in straight ahead and steady turning conditions. The viscous flow field of the fully discretized waterjet – propelled vehicle is numerically solved utilizing RANS method. Drift angles ranging from 0° to 30° with an interval of 10° are considered. The theoretical control volume of waterjet system under oblique flow and the corrected thrust equation are proposed. The results show that the enhanced bilge vortex in drift alters the ingested flow pattern of the waterjet-propelled vehicle. A steady hydraulic performance of the pump is observed under non-cavitating conditions, and the inlet is one of the major source of the energy loss of the internal flow. It is problematic to evaluate the thrust and the inlet efficiency due to the irregular shape of capture area. The tangential velocity component is in proportion to the drift angle at pump inflow plane, and leads to the port/starboard asymmetry of the axial velocity and vorticity. The swirling flow rolls up near the windward inlet duct and local vortices align to the spiral axial flow. The streamwise vortex occurs and distributes near the lower-windward side of the inlet in steady turning conditions.

Anemia Detection with Contrast-enhanced Photon-counting CT

HomeRadiologyVol. 305, No. 2 PreviousNext CommunicationsFree AccessErratumAnemia Detection with Contrast-enhanced Photon-counting CTJonathan D. Dodd, Roisin MacDermottJonathan D. Dodd, Roisin MacDermottJonathan D. DoddRoisin MacDermottPublished Online:Oct 24 2022https://doi.org/10.1148/radiol.229023MoreSectionsPDF ToolsImage ViewerAdd to favoritesCiteTrack CitationsPermissionsReprints ShareShare onFacebookTwitterLinked In Originally published in:https://doi.org/10.1148/radiol.221471Erratum in:https://doi.org/10.1148/radiol.229023The quote on the first page was changed to read …became clearly visible on noncontrast CT images in canine hearts. The dose-length product unit was changed to mGy ∙ cm, and the associated value was changed from 59 to 592. Reference 4 DOI was changed to https://doi.org/10.1148/radiol.220063.Article HistoryPublished online: Oct 24 2022Published in print: Nov 2022 FiguresReferencesRelatedDetailsAccompanying This ArticleAnemia Detection with Contrast-enhanced Photon-counting CTJul 26 2022RadiologyRecommended Articles Influence of Heart Rate on Image Quality and Radiation Dose Exposure in Coronary CT AngiographyRadiology2021Volume: 300Issue: 3pp. 701-703Slow and Steady Wins the Race: Lower Heart Rates Improve Diagnostic Quality for Coronary CT AngiographyRadiology2021Volume: 300Issue: 3pp. 704-705Radiation Dose Reduction by Using CT with Iterative Model Reconstruction in Patients with Pulmonary Invasive Fungal InfectionRadiology2018Volume: 288Issue: 1pp. 285-292Evaluation of Kidney Stones with Reduced–Radiation Dose CT: Progress from 2011−2012 to 2015−2016—Not There YetRadiology2017Volume: 286Issue: 2pp. 581-589MRI of Iron Oxide Nanoparticles and Myeloperoxidase Activity Links Inflammation to Brain Edema in Experimental Cerebral MalariaRadiology2018Volume: 290Issue: 2pp. 359-367See More RSNA Education Exhibits Usefulness of Spiral Flow Tube for Saline Chaser Capable of Improving Visualization Ability of Subclavian Artery in Cervical CT AngiographyDigital Posters2019Optimization of One-beat 256 Row Detector Coronary CT Angiography Using Low Contrast Media Protocols in Patients with Free Breathing under Automatic Tube Voltage SelectionDigital Posters2018Coronary CT Angiography with Wide Coverage Detector: How to Optimize Contrast Injection and Scan Protocol Based on Patient Size to Reduce Contrast and Radiation DosesDigital Posters2018 RSNA Case Collection Cardiac MyxomaRSNA Case Collection2020Chiari 1 malformation RSNA Case Collection2020Epiploic AppendagitisRSNA Case Collection2022 Vol. 305, No. 2 Metrics Altmetric Score PDF download

Heat transfer enhancement of water-cooled triply periodic minimal surface heat exchangers

Whether triply periodic minimal surface (TPMS) heat exchangers are applicable to cooling or cold storage systems as a cooler for supercritical carbon dioxide (SCO2) is undocumented. Here the conjugated heat transfer of SCO2 in TPMS Schoen-G heat exchanger and printed circuit heat exchanger (PCHE) was predicted based on three-dimensional steady turbulent Reynolds-averaged Navier-Stokes equations, energy equation and shear stress transport model using computational fluid dynamics software ANSYS CFX when SCO2 inlet temperature and pressure vary in 65–30 ℃ and (8–9)MPa. SCO2 in two heat exchangers is cooled under counter-flow conditions by a stream of cold water with given inlet temperature and mass flow rate. It was shown that the mean heat transfer coefficient of SCO2 in TPMS Schoen-G heat exchanger is larger than PCHE. As the inlet pressure rises, the friction factor increases and Nusselt number decreases in the heat exchangers due to decreased Reynolds number and Prandtl number, respectively. The friction factor ratio, Nusselt number ratio and performance evaluation criterion vary in the range of 0.38–0.50, 1.07–1.49, and 1.45–2.04 with Reynolds number and inlet temperature when the PCHE serves as a reference heat exchanger. The streamlines in TPMS Schoen-G heat exchanger are quite smooth even though the areas with a higher velocity appear. The streamlines in PCHE exhibit a spiral flow pattern to result in extra hydraulic loss. The heat transfer enhancement of TPMS Schoen-G heat exchanger is much better TPMS Schwarz-D heat exchanger at a Reynolds number higher than 16,000. The enhancement is attributed to a larger heat transfer surface area and more topological tortuosity without flow separation than PCHE.

Mission as Withness

Spiral mobility or flow is a good metaphor for contemporary global experience. Today’s life is precariously shaped by incessant cyclical movement from apocalypse to ‘post-apocalypse’ and from one post-apocalypse to another. There is no indication of what may be expected of the future. The future is in chaos. It appears that we are living through chaotic end times rather than experiencing mere gestures of the end times. A perpetual apocalypse seems the best way to describe the current reality. Therefore, Covid-19 seems to have been nothing but a mere reminder that we are on a sinking lifeboat. This article argues that in such an ever-wounded God’s world, African Pentecostalism has to shift the gear from mission as witness to mission as withness. The withness missiology can help in the process of re-discovering the theological and missiological meaning of life in an ever-wounded world and alternative ways of intercarnating into one another for the sake of common basic good of flourishing. It concludes that God’s Church is pneumatologically intended toward God’s world.

Hydrodynamics-driven community coalescence determines ecological assembly processes and shifts bacterial network stability in river bends

Community coalescence, i.e., the mixing and merging of microbial communities and their surrounding environments, is prevalent in various ecosystems and potentially acts on ecological processes. River bends are distinguished by significant cross-stream velocities and spiral flow. The flow in river bends causes the mixing of microbial communities, thus making the resultant community (after mixing) different from its precursors (before mixing) through ecological processes. However, so far, no studies have explored the effect of community coalescence on ecological processes and network stability under the hydrodynamic processes of river bends. Here, we explored bacterial community assembly and community coalescence in river bends by coupling hydrodynamic profiling, aqueous biogeochemistry, DNA sequencing, and ecological theory. The results showed that the water flow dominated the community coalescence by regulating the movement of suspended sediments. The main ecological process determining the bacterial community compositions in water was the dispersal process, whereas in sediments it was the selection process. Furthermore, the negative cohesion results showed that community coalescence determined the stability of bacterial networks through competition and predation. This study depicted the bacterial community coalescence in river bends and highlighted their associations with network stability, which might provide new insights into bacterial community assembly and coalescence under complex hydrodynamics in the aquatic environment.

Characteristic of Spiral Displacement Process in Primary Cementing of Vertical Well Washout

Summary Cementation is an essential process in well drilling, which provides security and isolation for following operations and for wells’ long-life production. Irregularity of the wellbore makes cementing more complex, with displaced fluid becoming easily trapped and leading to poor isolation. Here, we investigated spiral displacement of washout, which is one kind of irregularity, where the spiral flow is induced by a cyclone centralizer. The features of spiral flow with sudden hole enlargement, differences between spiral and nonspiral displacement processes, and influence of some parameters were investigated with a simulation method. First, the induced radial flow is around zero (10−1) of the main flow, which is enough for displacing radially, and this radial flow results in radial migration and dispersion of flow field. Cooperating with reversing flow after hitting the outer wall, radial migration leads to flow field mixing and spiral velocity dissipating quickly along the axial direction. Moreover, spiral flow is beneficial for cementing of washout, and the displacing pattern with spiral flow is different compared with axis flow. In spiral displacement, cement slurry accumulates at the bottom and outer side of the washout, while accumulation happens at the top and inner side of the washout for nonspiral flow. The accumulation pattern in spiral displacement prompts movement of residual fluid, but topside accumulation hinders removal of that. Of these parameters, density difference can depress the elongation of the interface and has a positive effect on displacement. An increase in washout length and diameter has a favorable influence, as such enlargement allows for further development of displacing flow and delays the breakthrough. An increase in displacing velocity and rotation angle has a nonmonotonic effect in that with the displacing velocity increasing, the displacement first worsens, then improves, but increasing the rotation angle has the opposite effect.

A compact Double-spiral electromagnetic pump for liquid metal cooling

This paper reports a novel conception of the high-performance double spiral electromagnetic pump (DS-EMP) to efficiently drive liquid metal (LM) fluid with minimum volume. The mathematic model and experimental test methods have been adopted to investigate the driving characteristics of DS-EMP. The result shows that the performance of DS-EMP can be regulated by changing the number of the spiral flow channel. Increasing the number of spiral flow channels is conducive to achieving a high-pressure head. Reducing the number of spiral flow channels is beneficial for obtaining a large flow rate. The experimental result indicates that it can provide the maximum pressure head of 76.5 kPa @200A and the corresponding maximum flow rate of 2.19 L/min with a compact volume of 0.8 L. The LM cooling loop driven by DS-EMP was established to achieve efficient cooling of 156 W/cm2 (755 W) heat flux with a flow rate of 1.86 L/min.

Spiral Laminar Flow is Associated with a Reduction in Disturbed Shear in Patient-Specific Models of an Arteriovenous Fistula.

Areas of disturbed shear that arise following arteriovenous fistula (AVF) creation are believed to contribute to the development of intimal hyperplasia (IH). The presence of helical flow can suppress areas of disturbed shear, which may protect the vasculature from IH. Therefore, the aim of this study is to determine if helical flow, specifically spiral laminar flow (SLF), is present in patient-specific AVF models and is associated with a reduction in exposure to disturbed shear. FourAVF were imaged using MRI within the first two weeks following fistula creation. Patient-specific boundary conditions were obtained using phase-contrast MRI and applied at the inlet and outlets of each model. Computational fluid dynamics was used to analyse the hemodynamicsin each model and compare the helical content of the flow to the distribution of disturbed shear. BC-1 and RC-2 are characterised by the presence of SLF, which coincides with the lowest distribution of disturbed shear. Contrastingly, SLF is absent from BC-2 and RC-1 and experience the largest amount of disturbed shear. Interestingly, BC-2 and RC-1 developed an anastomosis stenosis, while BC-1 and RC-2 remained stenosis free. These findings are in agreement with previous clinical studies and further highlight the clinical potential of SLF as a prognostic marker for a healthy AVF, as its presence correlates with an overall reduction in exposure to disturbed shear and a decrease in the incidence of AVF dysfunction, albeit in a small sample size.

Extraction of Cu2+ from wastewater in a novel spiral microchannel

To effectively remove Cu2+ from wastewater, the extraction process of Cu2+ in a novel spiral microchannel was studied in this work. The effect of operating parameters and equipment structure parameters on Cu2+ extraction was systematically investigated, and the effect of various parameters on the extraction process were compared by parameter fitting. The synergistic enhancement of spiral flow field and ultrasonic field was studied and compared with other microchannel extraction of Cu2+. Under the optimum conditions of small curvature, small inner diameter, long tube length and low pitch, the extraction rate of Cu2+ reaches the equilibrium extraction rate of 73.99 %, the overall volumetric mass transfer coefficient can reach 4.36 s−1, and the space-time yield can reach 23761 L/(L·h). Compared with other devices, the overall volumetric mass transfer coefficient and space-time yield have been improved by an order of magnitude, proving the high efficiency of Cu2+ extraction in the spiral microchannel. This study has guiding significance for the efficient extraction of Cu2+ in microchannel and the design of microchannel structure.

Numerical Simulation of the Flow Pattern of Spiral Annular Flow with a Guide Strip by Spiral On-Way.

To study the gas–liquid two-phase spiral annular flow pattern and its conversion law in a horizontal tube with twist tape by spiral on-way, a numerical simulation is carried out using the RNG k-ε model, and the DPM model is adopted as the particle motion model. The research results show that three main flow patterns are obtained, which are spiraling churn flow, spiraling annular flow, and spiraling annular twine flow. The ratio of the liquid-phase to gas-phase velocity VL/VG is the main factor that affects the existence of the gas phase. When VL/VG > 1/2, the flow pattern is a spiral cluster flow; when 1/5 < VL/VG< 1/2, the flow pattern is a spiral annular flow; and when VL/VG < 1/5, the flow pattern is a spiral annular flow. Compared with the flow pattern of the local spiral flow pattern of the short twisted band, it was found that the occurrence conditions of annular flow were postponed and a new flow pattern appeared. The research results of this paper have guiding significance for the pipeline risk management of natural gas hydrates and the engineering application of the full rotation of guide strips.

Vortex-induced vibration of flexible riser transporting high-speed spiral flow in deep-sea mining

According to Hamilton's principle and a mechanical decomposition model proposed for high-speed spiral flow, vibration governing equations of flexible riser transporting high-speed spiral flow are developed for vortex-induced vibration (VIV) analysis for lifting pipe system in deep-sea mining. The classic van der Pol oscillator is used to simulate the dynamic characteristics of VIV. The governing equations are then discretized and solved by the finite element method and the Runge-Kuta method. Furthermore, dynamic characteristics of VIV of the flexible riser transporting straight flow and spiral flow are investigated and the effects of the spiral flow incidence velocity and angle controlled by the jet device on VIV responses are evaluated. Also, the VIV dynamics considering different damping ratios are examined. The results show that the rotational angular velocity of the spiral flow would amplify the mean deflection of the in-line (IL) direction, and the incidence velocity has a significant nonlinear effect on the dominant frequency of the riser, which would induce the high-order dominant vibration modes when the incidence velocity is large sufficiently. However, the incidence angle has relatively less effects on the VIV responses of flexible riser. Moreover, the locked interval of VIV is less influenced by damping ratio below 0.1.

Distributed encoding of curvilinear self-motion across spiral optic flow patterns

Self-motion along linear paths without eye movements creates optic flow that radiates from the direction of travel (heading). Optic flow-sensitive neurons in primate brain area MSTd have been linked to linear heading perception, but the neural basis of more general curvilinear self-motion perception is unknown. The optic flow in this case is more complex and depends on the gaze direction and curvature of the path. We investigated the extent to which signals decoded from a neural model of MSTd predict the observer’s curvilinear self-motion. Specifically, we considered the contributions of MSTd-like units that were tuned to radial, spiral, and concentric optic flow patterns in “spiral space”. Self-motion estimates decoded from units tuned to the full set of spiral space patterns were substantially more accurate and precise than those decoded from units tuned to radial expansion. Decoding only from units tuned to spiral subtypes closely approximated the performance of the full model. Only the full decoding model could account for human judgments when path curvature and gaze covaried in self-motion stimuli. The most predictive units exhibited bias in center-of-motion tuning toward the periphery, consistent with neurophysiology and prior modeling. Together, findings support a distributed encoding of curvilinear self-motion across spiral space.