Diagonal Flow Research Articles

Equidistribution of expanding degenerate manifolds in the space of lattices

AbstractFor the space of unimodular lattices in a Euclidean space, we give necessary and sufficient conditions for equidistribution of expanding translates of any real‐analytic submanifold under a diagonal flow. This work extends the earlier result of Shah in the case of nondegenerate submanifolds. We apply the above dynamical result to show that if the affine span of a real‐analytic submanifold in a Euclidean space satisfies certain Diophantine and arithmetic conditions, then almost every point on the manifold is not Dirichlet‐improvable.

Thermal performance comparison of vertical and diagonal flow configurations in corrugated plate heat exchanger

Thermal performance comparison of vertical and diagonal flow configurations in corrugated plate heat exchanger

Quantifying Compound and Nonlinear Effects of Hurricane‐Induced Flooding Using a Dynamically Coupled Hydrological‐Ocean Model

AbstractWe recently developed a dynamically coupled hydrological‐ocean modeling system that provides seamless coverage across the land‐ocean continuum during hurricane‐induced compound flooding. This study introduced a local inertial equation and a diagonal flow algorithm to the overland routing of the coupled system’s hydrology model (WRF‐Hydro). Using Hurricane Florence (2018) as a test case, the performance of the coupled model was significantly improved, evidenced by its enhanced capability of capturing backwater and increased water level simulation accuracy and stability. With four model experiments, we present a framework to detangle, define, and quantify compound and nonlinear effects. The results revealed that the flood peaks in the lower Cape Fear River Basin and the coastal waters were contributed by inland flooding and storm surge, respectively. These two processes had comparable contributions to the flooding in the Cape Fear River Estuary. The compound effect was identified when the flood levels resulting from the combination of land and ocean processes surpassed those caused by an individual process alone. The compound effect during Hurricane Florence exhibited limited impact on flood peaks, primarily due to the time lag between the peaks of the storm surge and the inland flooding. In the period between the two peaks, the compound effect was salient and significantly impacted the magnitude and variation of the flood level. The nonlinear effect, defined as the difference between the compound flood level and the superposition of storm surge and inland flooding water levels, reduced flood levels in the river channels while increasing flood levels on the floodplain.

Machine-learning and CFD based optimization and comprehensive experimental study on diagonal flow fan for energy conservation and efficiency enhancement

The diagonal flow fan, known for its innovative airflow guiding technique, presents a dual advantage of heightened efficiency and reduced noise levels. Despite garnering attention in energy production systems, research on optimizing outlet guide vanes for diagonal flow fan performance remains limited. This study introduces a novel machine learning approach, utilizing Opt LHD sampling instead of traditional simulations and experiments to accumulate ample sample data. The fusion of LS-SVM and improved GA-PSO is employed for multi-objective optimization of outlet guide vanes, aiming to simultaneously enhance fan performance and reduce energy consumption. Experimental assessments reveal the optimized fan's significant improvements, including a 106 Pa increase in total pressure, a 3.6 dB reduction in noise levels, and a remarkable 16.3% enhancement in total pressure efficiency. These results highlight the robustness of the machine learning approach in optimizing diagonal flow fan exit guide vanes, effectively addressing the research gap in this area. Additionally, numerical analysis of internal flow dynamics and acoustic properties pre and post-optimization uncovers the intrinsic mechanisms influencing the overall performance of the diagonal flow fan.

Re-Engineering Dew-Harvesting Cactus Macrostructures to Enhance Water Collection as an Adaptive Climate Change Strategy: An Experimental Comparison

The spinal structures found on Copiapoa cinerea var. haseltoniana, an efficient dew-harvesting cactus, were fabricated and evaluated both in a climate chamber and outdoors in dewy conditions. A mix of aluminium and steel was used to fabricate these surfaces, with aluminium being used for everything but the replicated spine features, which were constructed from steel. Each surface was entirely coated with a highly emissive paint containing an alumina–silicate OPUR additive. Three replica versions (stem only, spine only, and stem & spine) were compared to a flat planar reference surface. Experimental results demonstrated that all three biomimetic macro-structured surfaces significantly enhanced dew harvesting compared to the reference surface. It was established that the stem & spine replica, spine replica, and stem replica all demonstrated significantly more dew harvesting, with mean efficiency ratios in respect of the reference surface of 1.08 ± 0.03, 1.08 ± 0.02, and 1.02 ± 0.01, respectively. Furthermore, the method of surface water collection was found to influence the water collection rate. The diagonal run-off flow across a flat planar surface was 34% more efficient than the parallel run-off flow on the same surface. These findings provide valuable insights for the construction and installation of biomimetic-inspired dew-harvesting devices, particularly in regions that are most challenged by decreasing dew yields as a result of climate change.

Topological mixing of positive diagonal flows

Topological mixing of positive diagonal flows

The multi-objective optimisation design of outlet guide vanes of diagonal flow fan based on sobol sensitivity analysis

Diagonal flow fans offer substantial energy-saving potential and find broad application across various sectors. Their performance relies heavily on factors like outlet guide vanes and spacing relative to moving blades. However, research into enhancing fan performance through optimized guide vanes and spacing remains limited. In this study, we focus on improving the accuracy of predicting the internal flow field of diagonal flow fans. This paper incorporate rotation and curvature effects using the Large Eddy Simulation (LES) model and introduce stress terms with helicity constraints to create a non-linear subgrid-scale model. This refined model enables more precise numerical simulations. By employing accurate simulations, we optimize the outlet guide vane configuration and conduct sensitivity analysis. We utilize a Radial Basis Function (RBF) model coupled with the Sobol method for this purpose. The optimized guide vane design exhibits enhanced resistance to airflow separation compared to the original, resulting in notable reductions in flow losses within the grille channel. Experimental tests are performed on the diagonal flow fan both before and after optimization. At the specified operating point, the second guide vane optimization leads to a 1.28 m3/min increase in fan flow, a 4.33% rise in total pressure efficiency, and a 2.2 dB noise reduction. These findings underscore the accuracy of the helicity correction model in predicting diagonal flow fan behavior. The multi-objective optimization approach, combining the RBF proxy model with the Sobol method, proves highly reliable. It offers valuable design insights for similar fans and establishes a credible design methodology.

Shrinking target horospherical equidistribution via translated Farey sequences

For a certain diagonal flow on SL(d,Z)﹨SL(d,R) where d≥2, we show that any bounded subset (with measure zero boundary) of the horosphere or a translated horosphere equidistributes, under a suitable normalization, on a target shrinking into the cusp. This type of equidistribution is shrinking target horospherical equidistribution (STHE), and we show STHE for several types of shrinking targets. Our STHE results extend known results for d=2 and L﹨PSL(2,R) where L is any cofinite Fuchsian group with at least one cusp.The two key tools needed to prove our STHE results for the horosphere are a renormalization technique and Marklof's result on the equidistribution of the Farey sequence on distinguished sections. For our STHE results for translated horospheres, we introduce translated Farey sequences, develop some of their geometric and dynamical properties, generalize Marklof's result by proving the equidistribution of translated Farey sequences for the same distinguished sections, and use this equidistribution of translated Farey sequences along with the renormalization technique to prove our STHE results for translated horospheres.

Komunikasi Organisasi Dalam Meningkatkan Etos Kerja Pengurus Di Himpunan Mahasiswa Islam (Hmi) Cabang Sukabumi

Organizational communication is process of communication within formal and informal organizations in a more complex form. Organizational communication consists of vertical, horizontal and diagonal communication. In an organization, giving encouragement is included as a form of motivation that is carried out to increase the work enthusiasm of the board, so that it can achieve the goals and results desired by the organization. This study uses a qualitative method with a descriptive approach. The study of organizational communication flow at the Sukabumi branch of the Himpunan Mahasiswa Islam (HMI) did not all go well. Only Horizontal and Diagonal communication flows run smoothly. Vertical communication flow (from superiors to subordinates and vice versa) is still not effective. This greatly affects the work ethic which decreases and is not optimal.

The influence of hyporheic exchange with spur dikes: Laboratory experiments

It is important to understand heat transfer changes in the hyporheic zone of spur dikes when assessing ecological restoration and sustainability in rivers. To reveal the rule of hyporheic exchange under the action of a spur dike, the sinusoidal temperature change of surface water was set with a period of 24 h. The porous subsurface flow paths under different riverbed forms were plotted through dye tracing. In addition, the influences of surface water velocity (U), river width narrowing ratio (L/B), the number of spur dikes and riverbed shape on hyporheic exchange were also studied using the temperature tracing method. The results show that the hyporheic exchange path presents a trend of diagonal flow downstream, first conducting turbulent diffusion upstream and then sinking, with different riverbed morphologies having different path lengths. The temperature of surface water has a significant controlling effect on the temperature field of the riverbed. The sediment temperature change from the water–sediment interface to 0.3 m depth is closer to the sinusoidal trend. The change in surface water velocity (U) has the most significant effect on the temperature amplitude ratio. The temperature field below spur dikes is more susceptible to the impact of spur dikes and usually presents a “semielliptical” high-temperature area. With the increase in surface water velocity (U), river width narrowing ratio (L/B), and the number of spur dikes, the range of hyporheic exchange under the dam head also increases, which is positively related to the vertical section hyporheic exchange flux at the dam head. The local backwater area generated by spur dikes also affects pressure field distribution near spur dikes, but the changes caused by the fluctuation of the riverbed itself are greater than the impact of spur dikes on the riverbed. The water–sediment interface velocity at the spur dike increases sharply, and the upstream 1 m of the dam head gradually experiences upflow, drops sharply after reaching the maximum at the dam head, and then approaches zero after 1 m. There is no obvious upwelling and downwelling at the whole interface.

On the dimension drop conjecture for diagonal flows on the space of lattices

Let X=G/Γ, where G is a Lie group and Γ is a lattice in G, let U be an open subset of X, and let {gt} be a one-parameter subgroup of G. Consider the set of points in X whose gt-orbit misses U; it has measure zero if the flow is ergodic. It has been conjectured that this set has Hausdorff dimension strictly smaller than the dimension of X. This conjecture is proved when X is compact or when G is a simple Lie group of real rank 1. In this paper we prove this conjecture for the case G=SLm+n(R), Γ=SLm+n(Z) and gt=diag(ent,…,ent,e−mt,…,e−mt), in fact providing an effective estimate for the codimension. The proof uses exponential mixing of the flow together with the method of integral inequalities for height functions on SLm+n(R)/SLm+n(Z). We also discuss an application to the problem of improving Dirichlet's theorem in simultaneous Diophantine approximation.

A subspace theorem for manifolds

We prove a theorem that generalizes Schmidt’s Subspace Theorem in the context of metric diophantine approximation. To do so we reformulate the Subspace Theorem in the framework of homogeneous dynamics by introducing and studying a slope formalism and the corresponding notion of semistability for diagonal flows.

Komunikasi Organisasi Dinas Komunikasi Dan Informatika Kota Sukabumi

Organizational communication is one aspect that exists within the organization and talks about the transfer of information from a leader to subordinates, this is indicated by the existence of a communication flow consisting of vertical communication, horizontal communication, and diagonal communication, in order to achieve the goals of the organization it must be good communication carried out by employees so that the morale that is built will be higher. The work spirit that is built by all employees affects work productivity. The problem examined in this study is how the implementation of organizational communication flows is carried out by superiors to subordinates, subordinates to superiors, horizontal communication and diagonal communication occur, this is related to the four communication flows proposed by Ha-run (2008: 45) and various obstacles found in the implementation of organizational communication. The aim is to find out the implementation of the communication flow proposed by Harun. This research uses a qualitative case study approach. Based on the data obtained in the field, it shows that not all organizational communication delivery flows are not implemented properly, entirely, only two streams are mastered, namely vertical and horizontal communication, while diagonal communication flows in media channels cannot be seen to be used properly so that even when used the result is less effective and this has an impact on morale which should be high to be less than optimal.

Association of Left Ventricular Systolic Function with Diagonal Branch Flow in Patients with First Anterior ST-Elevation Myocardial Infarction Treated with Primary Angioplasty

Background: There are few studies about the impact of diagonal branch blood flow on echocardiographic findings in patients with first acute anterior myocardial infarction undergoing primary angioplasty. Objectives: We aimed to compare left ventricular systolic function measures in patients with first acute anterior ST-segment elevation myocardial infarction (STEMI) treated with primary angioplasty based on diagonal branch blood flow after the procedure. Methods: This study was a single-center study that enrolled patients with their first acute anterior STEMI treated with primary angioplasty in our center between October 2020 and March 2021. Patients were divided into two groups: The patients with final thrombolysis in myocardial infarction (TIMI) flow III in diagonal (sufficient diagonal flow) and patients with final TIMI flow less than III in diagonal (insufficient diagonal flow) after the procedure. The left ventricular Wall-Motion Score Index (WMSI) and left ventricular ejection fraction (LVEF) were compared between the two groups. Results: A total of 107 patients with first anterior STEMI treated with primary PCI were enrolled in the present study, of which 13 patients (12.1%) had insufficient diagonal flow after primary coronary angioplasty. The LVEF was lower in patients with insufficient diagonal flow (32.92 ± 7.29% vs. 39 ± 8.68%, P = 0.018). Also, this group had higher LV WMSI (1.68 ± 0.28 vs. 1.49 ± 0.26, P = 0.029). Conclusions: The present study showed that in patients with first acute anterior STEMI undergoing primary angioplasty, insufficient diagonal branch flow after the procedure was associated with worse left ventricular systolic function and higher LV WMSI.

Local Mixing of One-Parameter Diagonal Flows on Anosov Homogeneous Spaces

Abstract Let $G$ be a connected semisimple real algebraic group and $\Gamma < G$ be a Zariski dense Anosov subgroup with respect to a minimal parabolic subgroup. We prove local mixing of the one-parameter diagonal flow $\{\exp (t\mathsf {v}): t \in {\mathbb {R}}\}$ on $\Gamma \backslash G$ for any interior direction $\mathsf {v}$ of the limit cone of $\Gamma $ with respect to the Bowen–Margulis–Sullivan measure associated to $\mathsf {v}$. More generally, we allow a class of deviations to this flow along a direction $\mathsf {u}$ in some fixed subspace transverse to $\mathsf {v}$. We also obtain a uniform bound for the correlation function, which decays exponentially in $\|\mathsf {u}\|^2$. The precise form of the result is required for several applications such as the asymptotic formula for the decay of matrix coefficients in $L^2(\Gamma \backslash G)$ proved by Edwards–Lee–Oh.

Genericity on submanifolds and application to universal hitting time statistics

In this paper, we investigate Birkhoff genericity on certain submanifold of $X=SL_d(\bR)\ltimes (\bR^d)^k/ SL_d(\bZ)\ltimes (\bZ^d)^k$, where $d\geq 2$ and $k\geq 1$ are fixed integers. The submanifold we consider is parameterized by unstable horospherical subgroup $U$ of a diagonal flow $a_t$ in $SL_d(\bR)$. Under the assumption that the intersection of the submanifold with affine rational subspaces has Lebesgue measure zero, we show that the trajectory of $a_t$ along Lebesgue almost every point on the submanifold gets equidistributed on $X$. This generalizes the previous work of Frączek, Shi and Ulcigrai in \cite{Shi_Ulcigrai_Genericity_on_curves_2018}. Following the scheme developed by Dettmann, Marklof and Strombergsson in \cite{Marklof_Universal_hitting_time_2017}, we then deduce an application of our results to universal hitting time statistics for integrable flows.

Multi-Objective Optimization of Rear Guide Vane of Diagonal Flow Fan Based on Robustness Design Theory

As an essential fluid machine in national production, the optimal design of the performance of fans has long been a focus of research. In the format of small diagonal flow fans with rear guide vanes, there are too many design variables, and the design parameters interact with each other, resulting in a degradation of the fan’s performance under actual operating conditions. Under realistic conditions, many uncertainties exist in the object of study and fluctuations in variables and parameters lead to a specific deviation of the optimization target from the design target. A method is needed for the robust and optimal design of angular flow fans under stochastic operating conditions of the design variables. In this paper, a multi-objective aerodynamic performance powerful design method is proposed using Pearson correlation analysis, combined with CFD calculation method, Latin hypercube experimental design and the Kriging agent model, to optimize the rear guide vane structural parameters of the diagonal flow fan under uncertain aerodynamic performance conditions, analyze the flow field characteristics before and after the modification, and select the optimal design model for the release. The test results show that the total pressure of the optimized fan is increased by 86 Pa, and the noise is reduced by 2.4 dB. The proposed optimization method is effective and can also be used to optimize the performance of other types of fans.

Performance Optimization Design of Diagonal Flow Fan Based on Ensemble of Surrogates Model

Due to the advantages of a high total pressure coefficient, large flow coefficient, and high efficiency, the diagonal flow fan is widely used in people’s livelihood and industrial fields. However, the design of the diagonal flow fan is mostly empirical, multi-solution, and comprehensive. The traditional optimization design process often consumes huge computing resources. In this paper, the diagonal flow fan blade is parameterized, the design variables are determined, and the accuracy of the parameterization method is verified. The maximum fitting error is controlled at approximately 0.1%. Based on the parametric design of blades, this paper organically integrates the traditional Kriging model and RBF model, and introduces the Ensemble of surrogates model (ES) to verify that the ES model has higher prediction accuracy in the prediction of fan flow and total pressure efficiency than the traditional prediction model. Subsequently, the Pareto optimal solution set of the approximate model within the global design scope is searched by NSGA-II. The numerical simulation and experimental verification show that the actual flow of the fan increases by 10% and the efficiency of the full pressure increases by 3.2% under the design condition of the optimized blade. The optimized model can significantly improve its air performance.

Flow and Heat Transfer Simulation in a Complete Pressurized Water Reactor Fuel Assembly Using Wall-Modeled RANS

Abstract Reproduction of turbulent flow and heat transfer inside a pressurized water reactor (PWR) fuel assembly is a challenging task due to the complex geometry and the huge computational domain. Capability of a wall-modeled Reynolds-averaged Navier–Stokes (RANS) simulation approach has been examined, which had already been validated against the measurements of the MATiS-H experiment. The method is here expanded to a larger computational domain aiming to reproduce flow and thermal field in the entire PWR fuel assembly. Namely, in the first part of this study, wall-modeled RANS is performed in a relatively short section of the representative PWR fuel assembly containing one single mixing grid with an array of 15 × 15 fuel rods. Linear and nonlinear eddy-viscosity turbulence models have been applied; however no significant difference is observed in the predicted pressure drop in the fuel assembly. The obtained predictions revealed an interesting pattern of swirl flow as well as diagonal cross flow downstream the mixing grid, which is driven by the applied design of split-type mixing vanes. In the second part, the computational model is extended to a domain representative of a complete PWR fuel assembly with ten mixing grids, inlet and outlet sections. Pressure drop and flow field are analyzed together with the predicted temperature and potential hot spots. In spite of a relatively coarse spatial resolution of the applied approach, the wall-modeled RANS provided promising results at least for the qualitative prediction of the pressure, flow field, and location of hot spots.

Stator modification methods for diagonal flow fans to achieve noise reduction of rotor-stator interaction

Stator modification methods for diagonal flow fans to achieve noise reduction of rotor-stator interaction