Approximate approach for improving pressure attenuation accuracy during hydraulic transients

The quasi-steady friction model is generally adopted in water hammer simulation in pipe network systems, which cannot accurately reflect the attenuation of pressure, while the existing unsteady friction model is challenging to use in complex pipe network systems. In this study, a convenient method for treating the friction term is proposed based on the Moody diagram. The attenuation process of water hammer pressure can be accurately reflected by reading the relationship curve between Reynolds number and the Darcy friction factor in the pipeline transient process. Combined with the classical water hammer experiment and the long pipe valve closing experiment in our laboratory, the accuracy of this model is verified, and the influence of absolute roughness (e) and Reynolds number (Re) on the model was analyzed as well. The results show that the pressure attenuation using the Method of Characteristics (MOC) and the proposed friction model has a good agreement with the experimental data. The absolute roughness has little influence on the results in hydraulically smooth pipe, while the minimum Reynolds number has a significant influence. When selecting the minimum Reynolds number, 2% ∼ 5% of the initial flow rate is recommended for calculation.

Complex singularity analysis for vortex layer flows

We study the evolution of a 2D vortex layer at high Reynolds number. Vortex layer flows are characterized by intense vorticity concentrated around a curve. In addition to their intrinsic interest, vortex layers are relevant configurations because they are regularizations of vortex sheets. In this paper, we consider vortex layers whose thickness is proportional to the square-root of the viscosity. We investigate the typical roll-up process, showing that crucial phases in the initial flow evolution are the formation of stagnation points and recirculation regions. Stretching and folding characterizes the following stage of the dynamics, and we relate these events to the growth of the palinstrophy. The formation of an inner vorticity core, with vorticity intensity growing to infinity for larger Reynolds number, is the final phase of the dynamics. We display the inner core's self-similar structure, with the scale factor depending on the Reynolds number. We reveal the presence of complex singularities in the solutions of Navier–Stokes equations; these singularities approach the real axis with increasing Reynolds number. The comparison between these singularities and the Birkhoff–Rott singularity seems to suggest that vortex layers, in the limit $Re\rightarrow \infty$ , behave differently from vortex sheets.

Aeolian Sand Dune Sedimentary Architecture Is Key in Determining the “Slow-Gas Effect” during Gas Field Production Performance

Summary Aeolian deposits are typically considered to act as homogeneous “tanks” of sand, which do not contain significant heterogeneities that impact the production of hydrocarbons. However, a succession of deeply buried aeolian gas reservoirs from the Permian Rotliegend exhibit a characteristic production decline profile that is typified by high initial flow rates, followed by a rapid decline in bottomhole pressure and decline in flow rate, subsequently followed by stabilization at low flow rates for an extended period (over several decades). This effect has been termed here as the “slow-gas effect,” and this production phenomenon has previously been attributed to structural compartmentalization. This paper presents an alternative, sedimentological hypothesis for the cause of the slow-gas effect based upon facies-controlled permeability differences within aeolian dune trough architectures. To test this, three interwell (km) scale models from well-studied aeolian analogs from Utah and Arizona were modeled with standard geostatistical reservoir techniques and populated with petrophysical properties from producing Rotliegend reservoirs in Germany. These models were subsequently dynamically simulated to analyze production behavior and test whether a similar “slow-gas” production profile could be reproduced. This study finds that the slow-gas effect primarily results from heterogeneities created by the complex interaction of deposition, accumulation, and erosion within aeolian strata, as opposed to the structural compartmentalization of homogeneous tanks of sand as previously thought. Structural compartmentalization and baffling through faulting where present will have an impact on fluid flow; however, it is not considered here to be the primary cause of the slow-gas effect. Results of this work demonstrate the necessity of accurately characterizing and reproducing low permeability heterogeneity in aeolian systems. These heterogeneities can either be modeled explicitly through the use of geostatistical reservoir modeling techniques as done here, or implicitly through the use of characteristic length and transmissibility multipliers. These results have significant implications on our understanding of how tight aeolian systems produce; namely, after depletion of the near-wellbore volume, production from the surrounding reservoir is baffled by a hierarchy of low permeability bounding surfaces and associated transmissibility barriers. Application for enhancing reservoir depletion strategies include optimizing well trajectories to maximize the number of dune penetrations and percentage of net reservoir facies in communication to the well; maximizing the size of the primary reservoir compartment. Neighboring wells should be placed in separate compartments to maximize the amount of fast-flowing gas production during the early production stage. Pressure management can be used to cyclically produce, deplete, and recharge the primary reservoir compartment to manage and optimize recovery during the decline phase and production tail.

Research on Numerical Simulation and Optimization of SCR Flow Field of 200MW Coal-Fired Unit

In this paper, Computational Fluid Dynamics (CFD) and Flow Model Test are applied to study the flow field of 200MW coal fired power plant, then the optimization program is proposed. Firstly, this paper summarizes some essential design points for SCR reactor system with different structures and different characteristic. Then, the initial flow field of the SCR reactor was simulated to find the defect by the Fluent. Then, optimize the flow fields of velocity of SCR system by adding splitters. In order to improve the mixing degree of flue gas and ammonia, Ammonia Injector Grids (AIG) was designed on the basis of the structure of SCR reactor. Considering the pressure loss and installation space were within allowed limits, a new static mixer was designed to optimize the flow fields of concentration. Through the shift of size, angle and altitude of the static mixer, this paper got a best design project. The research results can provide theoretical support and engineering guidance for the transformation and optimization of the new SCR denitration engineering reaction system.

Zeolite/Cerium Oxide Coat-on Activated Alumina Ball for Arsenite Removal via Fixed- Bed Continuous Flow Adsorption Column

Arsenite (As(III)) has threatened human life for ages. It is a necessity to remove As(III) from the contaminated water before general use. With the improvement of adsorption, higher As(III) removal can be achieved. This study aimed to develop zeolite/cerium oxide coat-on activated alumina ball adsorbent (CeZ-ball) with the aid of PVA binder and apply it to a fixed-bed continuous flow column for As(III) adsorption. The coating percentage of CeZ-ball was studied. Cerium ions leaching from CeZ-ball were monitored throughout the 2,880-min-column run to confirm the stability of CeZ attached to an activated alumina ball. Surface area, pH point of zero charge, and structural property of CeZ-ball were characterized. An average CeZ coating of 83.3% and rare leaching of cerium proved the coating method. The models proposed by Yoon-Nelson provided the most satisfactory fit with the breakthrough curve (r2 = 0.985, MPSD = 2.547, and q0 = 3.481 mg·g–1) under experimental conditions of the flow rate of 5 mL·min–1, As(III) influent concentration of 1 mg·L–1, and CeZ-ball weight of 40 g. The half-time of breakthrough (τ) was 1,228.739 min. The effects of the key parameters, including initial adsorbent weight, initial flow rate, and initial As(III) concentration, were investigated for the performance of As(III) adsorption. Simulated from the Yoon-Nelson model, the τ increased as well as the adsorbent weight but decreased as the flow rate increased, thus impacting the As(III) concentration. With the optimal condition, the fixed-bed continuous column with CeZ-ball could be used in As(III) removal from contaminated water.

A Method for Solving Percolation Overflow Boundary Based on Maximum of Horizontal Energy Loss Rate

The determination of overflow boundary is a prerequisite for the accurate solution of the seepage field by the finite element method. In this paper, a method for solving overflow boundary according to the maximum value of horizontal energy loss rate is proposed, which based on the analysis of the physical meaning of functional and the water head distribution of seepage field under different overflow boundaries. This method considers that the overflow boundary that makes the horizontal energy loss rate reach the maximum value is the real boundary overflow. Compared with the previous iterative computation method of overflow point and free surface, the method of solving overflow boundary based on the maximum horizontal energy loss rate does not need iteration, so the problem of non-convergence does not exist. The relative error of the overflow points is only 1.54% and 0.98% by calculating the two-dimensional model of the glycerol test and the three-dimensional model of the electric stimulation test, respectively. Compared with the overflow boundary calculated by the node virtual flow method, improved cut-off negative pressure method, initial flow method, and improved discarding element method, this method has a higher accuracy.

Is Nature Truly Healing Itself? Spontaneous Remissions and Clonal Replacement in Paroxysmal Nocturnal Hemoglobinuria

Paroxysmal nocturnal hemoglobinuria (PNH) is considered to be curable only through the means of allogeneic HSCT. One of the many fascinating and scientifically instructive aspects of the pathogenesis of this disease is the rare possibility of its spontaneous remission with disappearance of PNH clone and abatement of clinical symptoms, which has always captivated the research community. Due to the orphan nature of the condition, no clinical predictors have been identified so far as harbingers of this phenomenon. In a classical scenario, exhaustion of PNH clone may be associated with reappearance of aplastic anemia (AA), in which PNH clone reflects a semi-maladaptive attempt of recovery. Consequently, one could stipulate that the retraction of PNH clone(s) would have to be associated with a compensatory re-expansion of normal hematopoiesis should normal counts be maintained. The recent insights into the AA/PNH pathobiology shed light onto molecular underpinnings of polyclonal vs oligoclonal hematopoiesis and their dynamics. Here, through application of NGS we attempted to better discern the mechanism of PNH spontaneous remission taking advantage of our internal cohort of PNH patients. Among 92 patients with a diagnosis of hemolytic PNH (M:F ratio 0.88, median age 38 years, range 9-84) 41% were primary PNH (pPNH) while 59% were secondary to AA (sPNH). Overall, patients were clinically followed-up for a median time of 68 months (2-339). Median granulocyte clone size was 73% (22-99) with the majority of cases being classified as having a type III dominant red blood cells (RBCs) clone (80%) while 20% type II. Within this cohort, a total of 3 patients underwent spontaneous remission. UPN1 was a 69-year-old male diagnosed with pPNH at the age of 46 after an episode of deep vein thrombosis. He had been managed with prednisone, transfusions and anti-coagulation because of recurrent thrombotic episodes. Once available, he was started on eculizumab and later continued on ravulizumab. His initial flow cytometry study revealed the presence of a type III RBCs clone of 40% and a granulocyte clone of 89%. After 9 years of anti-complement therapy, the patient's clone started a slow decrease and the most recent study revealed a granulocyte clone of 0.02%. Molecular analysis performed at the time of eculizumab start showed a co-dominant mutational configuration by variant allelic frequency (VAF) with PIGA deletion (p.94_95del; VAF 29%) and a BCOR nonsense (p.Y1446X; VAF 27%). No HLA class I/II mutations were found in two longitudinal samples collected 1 year before and after eculizumab start. However, at the last sequencing performed after the complete disappearance of the PNH clone, the patient developed ASXL1 (p.E635Rfs*, VAF 26%) and ZRSR2 (p.E120Gfs*, VAF 42%) mutations along with retraction of the previous PIGA lesion. No decrease in blood counts was noted. UPN2 was a 58-year-old male initially diagnosed with severe AA at the age of 48 and treated with ATG + CsA. At that time, he had a co-existing PNH granulocyte clone of 28%. After 1 year from IST his PNH clone dropped to 1% and since then has been consistently below 1%. Patient has never received anti-complement therapy. At the time of PNH clone retraction, no HLA class I/II or myeloid driver mutations were found and PIGA mutations were not detectable. However, longitudinal molecular studies performed after disappearance of PNH clone revealed the acquisition of ASXL1 p.Q512X mutation at an initial VAF of 23%, which doubled (45%) at last follow-up 5 years later while normal counts persisted. UPN3 was instead a 59-year-old lady diagnosed with pPNH at the age of 30. She had a granulocyte clone as high as 43% with a type II RBCs clone of 17% and a typical PIGA splice site c.981+1G>A mutation (VAF 15%). She was initially treated with transfusions and steroids and her course was complicated by a cerebral venous sinus thrombosis. Patient was eventually given eculizumab and her PNH clone started decreasing until it vanished (last 0.04%) after 8 years. Analysis of samples prior to and after PNH disappearance did not show any HLA class I/II nor myeloid driver gene mutations with absence of PIGA alterations at last sequencing. PNH spontaneous remissions are rare events. In addition to be replaced by polyclonal hematopoiesis, PIGA clones may be swept by CHIP lesions in myeloid genes (e.g. ASXL1) characterized by improved fitness advantage in a process of Darwinian selection. Figure 1 Figure 1. Disclosures Maciejewski: Regeneron: Consultancy; Novartis: Consultancy; Bristol Myers Squibb/Celgene: Consultancy; Alexion: Consultancy.

Swirling to improve heat transfer in the MHD flow of liquid metal in a duct

The subject of this study is the effect of the initial “swirling” of the flow by installing cylindrical elements in the initial flow region affected by strong magnetic field. In particular, various designs (longitudinal, transverse, and inclined arrangement with respect to the magnetic field) and the dimensions of the cylinders are considered. To create liquid metal systems that are more predictable and possibly more efficient from the point of view of thermal hydraulics, we experimentally studied the flow in a rectangular channel with dimensions of 56×16 mm. For the first time, it was found that the presence of an initial flow disturbance leads to significant changes in the flow at a significant length (700 mm).

Characterization of milkweed-seed gust response

Inspired by the reproductive success of plant species that employ bristled seeds for wind-borne dispersal, this study investigates the gust response of milkweed seeds, selected for their near-spherical shape. Gust-response experiments are performed to determine whether these porous bodies offer unique aerodynamic properties. Optical motion-tracking and particle image velocimetry (PIV) are used to characterize the dynamics of milkweed seed samples as they freely respond to a flow perturbation produced in an unsteady, gust wind tunnel. The observed seed acceleration ratio was found to agree with that of similar-sized soap bubbles as well as theoretical predictions, suggesting that aerodynamic performance does not degrade with porosity. Observations of high-velocity and high-vorticity fluid deflected around the body, obtained via time-resolved PIV measurements, suggest that there is minimal flow through the porous sphere. Therefore, despite the seed’s porosity, the formation of a region of fluid shear, accompanied by vorticity roll-up around the body and in its wake, is not suppressed, as would normally be expected for porous bodies. Thus, the seeds achieve instantaneous drag exceeding that of a solid sphere (e.g. bubble) over the first eight convective times of the perturbation. Therefore, while the steady-state drag produced by porous bodies is typically lower than that of a solid counterpart, an enhanced drag response is generated during the initial flow acceleration period.

The California Environmental Flows Framework: Meeting the Challenges of Developing a Large-Scale Environmental Flows Program

Environmental flow programs aim to protect aquatic habitats and species while recognizing competing water demands. Often this is done at the local or watershed level because it is relatively easier to address technical and implementation challenges at these scales. However, a consequence of this approach is that ecological flow criteria are developed for only a few areas as dictated by funding and interest with many streams neglected. Here we discuss the collaborative development of the California Environmental Flows Framework (CEFF) as an example process for developing environmental flow recommendations at a statewide scale. CEFF uses a functional flows approach, which focuses on protecting a broad suite of ecological, geomorphic, and biogeochemical functions instead of specific species or habitats, and can be applied consistently across diverse stream types and spatial scales. CEFF adopts a tiered approach in which statewide models are used to estimate ecological flow needs based on natural functional flow ranges, i.e., metrics that quantify the required magnitude, timing, duration, frequency, and/or rate-of-change of functional flow components under reference hydrologic conditions, for every stream reach in the state. Initial flow needs can then be revised at regional, or watershed, scales based on local constraints, management objectives, and available data and resources. The third tier of CEFF provides a process for considering non-ecological flow needs to produce a final set of environmental flow recommendations that aim to balance of all desired water uses. CEFF was developed via a broad inclusive process that included technical experts across multiple disciplines, representatives from federal and state agencies, and stakeholders and potential end-users from across the state. The resulting framework is therefore not associated with any single agency or regulatory program but can be applied under different contexts, mandates and end-user priorities. The inclusive development of CEFF also allowed us to achieve consensus on the technical foundations and commitment to applying this approach in the future.