An efficient diffusion transformer-based method for reconstructing three-dimensional turbulent flows from two-dimensional observations

Experiment was conducted in a laboratory flume to measure the 3D turbulent flow field by an acoustic Doppler velocimeter in a scour hole at a 45? wing-wall abutment under a clear water regime. The profiles of time-averaged velocity components, turbulence intensity components, turbulent kinetic energy and Reynolds stresses at different azimuthal planes are presented. In the upstream, vector plots of flow field at azimuthal and horizontal planes show the presence of a large primary vortex associated with a downflow within the scour hole. In the downstream, the flow is upward. The bed shear stresses within the scour hole are estimated from the Reynolds stresses and the velocity gradients. The data presented in this study would be useful to the researchers for the future development and validation of theoretical models of flow field in a scour hole at bridge abutments

The subject of this paper is a flow-adaptive measurement grid algorithm developed for one-dimensional (1D) and two-dimensional (2D) flow field surveys with pneumatic probes in turbomachinery flows. The algorithm automatically determines the distribution and the amount of measurement points needed for an approximation of the pressure distribution within a predefined accuracy. The algorithm is based on transient traverses, conducted back and forth in the circumferential direction. A correction of the dynamic response is applied by deconvolving the transient measurement data using the information embedded in both transient measurements. In consequence, the performance of the algorithm is largely independent of the transient traversing speed and the geometry of the pressure measuring system. Insertion and removal strategies are incorporated in order to reduce measurement points and increase robustness toward differing flow field conditions. The performance of the algorithm is demonstrated for 2D flow field surveys with a pneumatic five-hole probe in an annular cascade wind tunnel. The measurement grid points are automatically adjusted so that a consistent resolution of the flow features is achieved within the measurement domain. Furthermore, the application of the algorithm shows a significant reduction in the number of measurement points. Compared to the measurement duration based on uniform grids, the duration is reduced by at least 7%, while maintaining a high accuracy of the measurement. The purpose of this paper is to demonstrate the performance of measurement grids adapted to local flow field conditions. Consequently, valuable measurement time can be saved without a loss in quality of the data obtained.

Numerical study on the performance of a novel three-dimensional stepped wavy flow field in PEMFC

In order to measure a complicated unsteady 3D subsonic turbomachinery flow field by use of five-hole pressure probes and a multisensor hot-wire probe, a computer aided measurement system was built up and developed. Long experiences acquired by us and by other research institutes in various experimental studies were taken into consideration as measurement rules in the system. Using the present measurement system, the 3D unsteady flow fields in turbumachinery were determined. The automatic measurements were performed satisfactorily even in the downstream rotor flow region. From the experiments, it is concluded that the quality of the measurements of the unsteady 3D flow field behind a rotor is improved greatly by means of the proposed computer aided multisensor system.

ABSTRACTUpdating of reservoir models by history matching of 4D seismic data along with production data gives us a better understanding of changes to the reservoir, reduces risk in forecasting and leads to better management decisions. This process of seismic history matching requires an accurate representation of predicted and observed data so that they can be compared quantitatively when using automated inversion. Observed seismic data is often obtained as a relative measure of the reservoir state or its change, however. The data, usually attribute maps, need to be calibrated to be compared to predictions. In this paper we describe an alternative approach where we normalize the data by scaling to the model data in regions where predictions are good. To remove measurements of high uncertainty and make normalization more effective, we use a measure of repeatability of the monitor surveys to filter the observed time‐lapse data.We apply this approach to the Nelson field. We normalize the 4D signature based on deriving a least squares regression equation between the observed and synthetic data which consist of attributes representing measured acoustic impedances and predictions from the model. Two regression equations are derived as part of the analysis. For one, the whole 4D signature map of the reservoir is used while in the second, 4D seismic data is used from the vicinity of wells with a good production match. The repeatability of time‐lapse seismic data is assessed using the normalized root mean square of measurements outside of the reservoir. Where normalized root mean square is high, observations and predictions are ignored. Net: gross and permeability are modified to improve the match.The best results are obtained by using the normalized root mean square filtered maps of the 4D signature which better constrain normalization. The misfit of the first six years of history data is reduced by 55 per cent while the forecast of the following three years is reduced by 29 per cent. The well based normalization uses fewer data when repeatability is used as a filter and the result is poorer. The value of seismic data is demonstrated from production matching only where the history and forecast misfit reductions are 45% and 20% respectively while the seismic misfit increases by 5%. In the best case using seismic data, it dropped by 6%. We conclude that normalization with repeatability based filtering is a useful approach in the absence of full calibration and improves the reliability of seismic data.

In this paper, we consider the reconstruction of 3D turbulent flow fields from a time series of lidar data in a conventionally neutral atmospheric boundary layer (CNBL). For the reconstruction we use the maximum a posteriori estimate of the flow field. This corresponds to an optimization problem, with a cost function that has two contributions; a first term originating from the prior belief on the probability of having a certain turbulent flow field without any observations. Flow field fluctuations are assumed normally distributed and thus statistically fully determined by the mean and two-point covariance of the velocity field. The second term, is related to the likelyhood of the observations, influenced by model and measurement uncertainties. The two-point covariance is computed and found to be significantly altered by the Coriolis force, breaking up longer streamwise velocity streaks and veering spanwise structures by ∼ 45° with respect to the mean flow direction. For the reconstruction, we consider two different scanning modes, a plan position indicator (PPI) mode and a trajectory which is based on a Lissajous curve. For the PPI scanning mode we find that the mean squared error of the reconstructed velocity field is around 10% of the background variance in the scanning plane, and quickly increases outside this region. The Lissajous curve on the other hand attains an average error of 40% over the scanning region, which spans almost the whole BL height.

Simulation of turbulent flows in an impingement dryer by an extended κ– ε model

To describe the structure of a flow field and understand the flow field image, limit streamlines must be extracted. In this paper, we propose a new intelligent method to extract them automatically. This method is also based on topological analysis, but has the ability to extract open limit streamlines that are not captured by conventional topology-based methods. Given a 2D flow field, we extend it firstly by vector mirroring around its boundary, and then detect and classify the critical points in the extended field. All saddles among the critical points are selected to compute limit streamlines. Contributing to the boundary extending, open limit streamlines, if any one exists, are included in the resulting lines as well as the closed ones. Furthermore, our method can find out limit cycles at the same time without any modification. Test results show that our method significantly improves the extraction of limit streamlines.

A novel 3D fine-mesh flow field design and performance analysis for proton exchange membrane fuel cells

Three-dimensional modelling of flow and reactive transport in heterogeneous porous media : M. A. Cushey, A. Bellin & Y. Rubin, in: Groundwater quality: remediation and protection. Proc. conference, Prague, 1995, ed K. Kovar & J. Krasny, (IAHS; Publication, 225), 1995, pp 257–261

Visual exploration of large and complex 3D steady and unsteady flow fields is critically important in many areas of science and engineering. In this paper, we introduce FlowGraph, a novel compound graph representation that organizes field line clusters and spatiotemporal regions hierarchically for occlusion-free and controllable visual exploration. It works with any seeding strategy as long as the domain is well covered and important flow features are captured. By transforming a flow field to a graph representation, we enable observation and exploration of the relationships among field line clusters, spatiotemporal regions and their interconnection in the transformed space. FlowGraph not only provides a visual mapping that abstracts field line clusters and spatiotemporal regions in various levels of detail, but also serves as a navigation tool that guides flow field exploration and understanding. Through brushing and linking in conjunction with the standard field line view, we demonstrate the effectiveness of FlowGraph with several visual exploration and comparison tasks that cannot be well accomplished using the field line view alone. We also perform an empirical expert evaluation to confirm the usefulness of this graph-based technique.

The study of fluid behaviors has been a challenging topic. Flow visualization enables us to visually acquire qualitative and quantitative flow information. There exist various software tools performing different flow visualization tasks. However, we lack tools that help students learn important flow field concepts. In this paper, we present a visualization app, named FlowVisual which runs on iOS devices, to illustrate basic flow field concepts in 3D. In order to meet a comprehensive learning goal for students, we integrate a number of techniques into FlowVisual design, including field-line tracing, field-line comparison, critical point detection and classification, template-based seeding, and surface visualization. We evaluate and demonstrate the effectiveness of FlowVisual by conducting a formal user study including an introduction and training session, an auto-grading test, and a post-questionnaire survey.

Three-dimensional flow phenomena have been observed in a shock tube experiment for shock waves and vortices by using an interferometric CT (Computed Tomography) technique with a N2 pulse laser. A model with small duct, which has a pair of circular open ends, is introduced in a test section of diaphragmless shock tube, and can be rotated around its central axis to change the observation angle. The projection image of density distribution for each observation angle is obtained by using a fixed Mach-Zehnder interferometer. Three-dimensional density distribution is reconstructed from these projection images. The shock Mach number is 2.3 in nitrogen gas of 19.4kPa initial pressure at the exits of the open ends. The resultant 3-D density flow fields are illustrated by several imaging technique to clarify 3-D features of shock waves, vortices, and their mutual interactions. A computational fluid dynamics (CFD) simulation is also applied to the 3-D flow fields. The CFD results can represent density and another properties in flow fields, and these properties are useful for identifying the phenomena. The mutual validation between the experimental CT density results and these CFD results is discussed. Three-dimensional features of flow fields are investigated in detail by analyzing the experimental CT results with CFD results.

Pictures of blockscale transport: Effective versus ensemble dispersion and its uncertainty

Multiresolution streamline placement is useful for interactive visualization of flow fields. In this paper, a new method is proposed to build placements of streamlines in different resolutions for 2D and 3D flow fields. This method is developed from