INSIGHTS INTO THE FLOW WITHIN THE WELL DOCK OF A MOTHERSHIP DURING FEEDER VESSEL DOCKING MANOEUVRES

An experimental campaign has been undertaken to explore the flow around a feeder vessel as it manoeuvres in and out of the well dock of a mothership. The parent hulls for this study are drawn from the floating harbour transhipper concept created by Sea Transport Corporation. Laser measurement techniques have been employed to analyse the flow field within the well dock while the feeder vessel both enters and departs. For the Master of the feeder vessel to safely perform these manoeuvres, the complex flows resulting from the highly confined nature of the well dock concept need to be understood and potentially mitigated. It is shown that the inclusion of vents in the well dock can significantly influence the flow and that their effectiveness is determined by the size of the vents. This study further progresses the authors’ recent work on the same novel concept where the confined water effect of the well dock and inclusion of vents is quantified for both the seakeeping behaviour and the docking/departure performance. It is concluded that the use of vents is very beneficial when a feeder vessel docks or departs the well dock, however a compromise on the vent size must be reached in order to reduce adverse effects on feeder vessel motions when docked and exposed to a seaway. It is likely that the optimum solution, that covers all operational parameters, only requires the inclusion of relatively small vents.

Multiple mass hierarchies from complex fixed point collisions

A pair of complex-conjugate fixed points that lie close to the real axis generates a large mass hierarchy in the real renormalization group flow that passes in between them. We show that pairs of complex fixed points that are close to the real axis and to one another generate multiple hierarchies, some of which can be parametrically enhanced. We illustrate this effect at weak coupling with field-theory examples, and at strong coupling using holography. We also construct complex flows between complex fixed points, including flows that violate the c-theorem.

Ultrasound PIV Uncertainty Quantification

Ultrasound Particle image velocimetry (UPIV) is a non-invasive flow measurement technique where acousticopaque flow tracers are injected into a working fluid and ensonified to create ultrasound images. These images are processed using PIV cross-correlation based algorithms to measure the velocity field (Kim et al., 2004). UPIV is useful for opaque flows, primarily where complex flows exist, accordingly, it is used in many industrial and clinical research applications such as studying intracardiac flow (Crase et al., 2007). Furthermore, the measurement provides suitable temporal and spatial resolutions for improved diagnostic metrics. Mentioned applications and the sensitive diagnostic industrial and clinical decisions made based on these measurements intensifies the importance of characterizing the UPIV measurement accuracy and associated uncertainty. However, quantifying UPIV measurement uncertainty is non-trivial due to the complexity of possible uncertainty sources, their combination, and propagation through the measurement chain. The formation of a particle image by ultrasound significantly differs from optical imaging, introducing unique aspects to image quality that must be considered. Particle images are formed across several ultrasound scan lines, yielding an elliptical particle image shape. Furthermore, the particle’s reflected pressure wave is converted to a digital signal that undergoes signal modulation, and this process forms a non-Gaussian point spread function (PSF) along the scan line direction. Additionally, clusters of tracers produce a single, bright image intensity and speckle image pattern. Compared to conventional PIV images, UPIV incurs significantly higher image noise due to lack of filtration for the ultrasound reflection of the non-tracer obstacles.

Disconnection and Reconnection as Resistance to Geosurveillance

Digital media has spawned entire industries centered on geosurveillance, resulting in complex flows of sensitive data. Practices surrounding the collection, use, and sale of this data are commonly concealed behind lengthy privacy policies riddled with legal jargon and devoid of technical specificity. Simultaneously, new methods of analysis tease out information from even “anonymized” data. As a result, it increasingly seems that the only reliable shelter from geosurveillance is to disconnect, but how difficult is this in practice, is it worth pursuing, and how might we do so? This chapter examines these questions. It first outlines several conceptualizations of privacy and establishes what is at stake every time privacy is eroded. It then overviews the many mechanisms that can produce geospatial data, illustrating the ubiquity of geosurveillance and difficulty of disconnection. Finally, and despite this difficulty, it discusses tactics for resistance, demonstrating that modern privacy requires not just disconnection, but reconnection.

Towards Reconstruction of Complex Flow Fields Using Unit Flows

Many complex turbulent flows in nature and engineering can be qualitatively regarded as being constituted of multiple simpler unit flows. The objective of this work is to characterize the coherent structures in such complex flows as a combination of constituent unitary flow structures for the purpose of reduced-order representation. While turbulence is clearly a non-linear phenomenon, we aim to establish the degree to which the optimally weighted superposition of unitary flow structures can represent the complex flow structures. The rationale for investigating such superposition stems from the fact that the large-scale coherent structures are generated by underlying flow instabilities that may be reasonably described using linear analysis. Clearly, the degree of validity of superposition will depend on the flow under consideration. In this work, we take the first step toward establishing a procedure for investigating superposition. Experimental data of single and triple tandem jets in crossflow are used to demonstrate the procedure. A composite triple tandem jet flow field is generated from optimal superposition of single jet data and compared against ‘true’ triple jet data. Direct comparisons between the true and composite fields are made for spatial, temporal, and kinetic energy content. The large-scale features (obtained from proper orthogonal decomposition or POD) of true and composite tandem jet wakes exhibit nearly 70% agreement in terms of modal eigenvector correlation. Corresponding eigenvalues reveal that the kinetic energy of the flow is also emulated with only a slight overprediction. Temporal frequency features are also examined in an effort to completely characterize POD modes. The proposed method serves as a foundation for more rigorous and robust dimensional reduction in complex flows based on unit flow modes.

PHANTOM MODEL OF DISTRIBUTION OF VIRAL OBJECTS IN A PANDEMIC. PART 3

The article states that the nature of the virus's interaction with objects during its spread in any environment is a significant problem. Therefore, taking into account the peculiarities of such a complex fractional composition of flows can make it possible to determine the nature of the interaction of the object, in particular biological, with complex particles of viral flows when touching. The author's previous works consider the peculiarities of the spread of viruses in the surrounding space of the pandanus zone of the object under the condition of a single fraction of the particle, ie in the near-surface layer. Of course, to better understand the nature of the interaction of viral flows with objects of possible infection, it is necessary to analyze the processes of virion’s touching to the cell surface of a biological object. The studied regularities of the occurrence of motion forces in environment’s space made it possible to determine the geometric parameters of the spread of viral formations near the object’s surface. The main purpose of this study was to continue to create a model of interaction of complex flows with different fractions that are carriers of viruses as material particles in the environment, in terms of modeling the motion and touching the surface of the object at different types of touch depending on their interaction. The mechanical movement of the virus during contact, rather than stages, as in biological processes, is considered. The nature of the interaction of complex viruses’s streams with objects of biological origin is modeled. To study the peculiarities of the interaction of the virion with the cell surface of a biological object, it is necessary to consider the flow complex of particles of different fractions, i.e. microstructures of virions that accompany drip suspension flows of body fluids and foreign dust particles. Thus, we can distinguish the motion of a complex of particles that comes into contact with object’s surface, as well as the possibility of breaking out individual microparticles, virions, which can emerge from the complex flow and propagate separately from others. At the same time, the dependences of the energy complex, which forms the flow of complex elements-particles of different fractions, which can take into account the range of flow propagation and features of motion kinematics, are determined. In further research, the phantom model of the propagation of fluxes of viral objects in space requires modeling the temporal parameters of the motion of fluxes of complex particles during the propagation to the object’s surface of various origins, including biological object.

Evaluation and application of advanced CFD models for rotating disc flows

This paper addresses limitations of widely used Reynolds-averaged turbulence models (RANS) for prediction of gas turbine internal air systems. Results from direct numerical simulation (DNS), wall-resolved large-eddy simulation (LES), wall-modelled large-eddy simulation (WMLES), and RANS for benchmark test cases are compared. For rotor-stator disc cavity flows results for mean velocities, velocity fluctuations, rotor torque and laminar-turbulent transition are considered and compared with published data. For cavities between co-rotating discs attention is focused on buoyancy-driven convection in the centrifugal force field. It is concluded that WMLES is suitable for application in engine conditions, offering better accuracy than RANS in some critical applications. This confirms recently published results for turbine rim sealing and is further illustrated by application to convection in a sealed cavity at higher Rayleigh number than is practical with DNS or wall-resolved LES. The results show that the approximate near-wall treatment gives reasonable results for complex flows and extend previous studies to higher speed rig conditions where Eckert number effects become significant.