Head Drop Research Articles

Performance characteristics of a contra-rotating pump-turbine in turbine and pump modes under cavitating flow conditions

Recent studies have indicated the potential of a contra-rotating pump-turbine (CRPT) as a low-head design that enables pumped hydro storage in regions with flat topography. However, the effects of cavitation have scarcely been investigated for the CRPT. The current paper utilises computational fluid dynamics simulations to study a model scale CRPT subjected to cavitating flow conditions to determine how cavitation affects the machine’s operating performance in both pump and turbine modes. In total, eight operating conditions have been evaluated for each mode. The inlet flow rate is considered fixed at 0.27 m3/s, while the outlet pressure is gradually changed to induce cavitating conditions. The study demonstrates that the pump mode operation of the CRPT is more sensitive to cavitation compared to the turbine mode. The pump mode operation shows a steady decline in efficiency with decreasing inlet pressure, whereas in turbine mode the efficiency settles at a lower level. The 3% head drop occurs at la Thoma number of 1.0 in pump mode and at 0.6 in turbine mode. At the 3% head drop, a large cavitating region is already present at the runner blades’ suction side of the runner closest to the lower reservoir in both modes. The large cavitating region causes the flow to separate from the runner blade surfaces, which explains the reduced operating performance. To ensure an almost cavitating-free operating condition and unaffected performance, the Thoma number needs to be above 1.0 in turbine mode and at least 1.5 in pump mode. A frequency analysis reveals that the presence of cavitation affects the dominant pressure pulsations in the system. A dynamic mode decomposition analysis is carried out, demonstrating that the non-trivial pressure pulsations are connected to the support struts.

Simulation and experimental analysis of fixed and rotating blades on the runner of Oryon Watermill applicable for head drops of the canal

Numerous sites for watermills exist in the world with shallow heads and are possible for power generation either mechanical or electrical. The prime mover required for the energy generation from such sites is in the developing phase with efficient, minimum components, and low cost as a modular unit. The Oryon Watermill (OWM) is one of them developed by Deepwater Energy applicable to water current directly. The working of OWM is used differently on the head drop of the canal with fixed and rotating blades using the NACA 6516 series of airfoil shapes as the novelty of this research. The research covers the CFD simulations with ANSYS Fluent 19.0 of two runners, fabrication, and conduction of tests on-site with a head drop of 1.2 m. The major variable was the water flow rate for both runners with the design discharge of 0.09 m3/s. The analysis of results showed the runner with rotating lamellas performed with 9% and 40% higher efficiency from the simulation and experiment respectively compared to the fixed type. The efficiency achieved from the research is at a low range indicating the availability of large space for future study on performance improvement.

Ketogenic Diet as a Therapeutic Intervention for Doose Syndrome: A Case Report and Review of Current Evidence

Epilepsy with myoclonic-atonic seizures, also known as Doose syndrome or myoclonic–astatic epilepsy (MAE), represents a challenging pediatric epilepsy syndrome, initially described by Doose et al. in 1970. MAE accounts for 1%–2.2% of juvenile-onset epilepsy cases, characterized by normal early development, followed by seizure onset between 7 months and 6 years. Seizure types include myoclonic, myoclonic-atonic, generalized tonic–clonic, and atypical absences, often accompanied by nonconvulsive status epilepticus. Electroencephalogram typically shows parietal-dominant rhythmic theta activity or a posterior 4 Hz pattern. While conventional antiseizure medications (ASMs) offer some efficacy, outcomes vary widely, and up to 50% of patients may experience refractory seizures and poor intellectual outcomes. The ketogenic diet (KD), a high-fat, low-carbohydrate diet inducing ketosis, has shown promise in reducing seizure frequency and severity in refractory epilepsy, including MAE. This case report describes a successful outcome with a South Indian style KD in a 3-year-old boy with Doose syndrome presenting with 20–25 daily head drop seizures despite multiple ASMs and steroid therapy. Initiation of a home-based KD utilizing traditional household ingredients significantly reduced seizure frequency by 60% within 1 month and 80% within 2 months and was 100% seizure-free in 3rd month following KD, alongside developmental improvements. The KD was well-tolerated, with improved nutritional status. This case underscores KD’s potential as a viable complementary therapy for MAE, emphasizing the need for ongoing parental support and supervision to ensure dietary adherence and optimize outcomes. It is commonly believed that the KD is challenging for the South Indian population to follow due to the high carbohydrate content in South Indian cuisine. However, this case demonstrates that a KD can indeed be tailored around South Indian dishes, highlighting the uniqueness of this approach. When the diet is customized to consider a child’s dietary habits, culture, and cuisine, it becomes easier to follow over the long term, leading to effective seizure control. Further research is necessary to refine dietary protocols and evaluate long-term efficacy in MAE management.

Numerical investigation of non-uniform inflow effects on internal and external characteristics of an axial-flow pump

This paper investigates the effects of non-uniform inflow on the internal and external characteristics of an axial-flow pump. Numerical simulation is employed to study two different configurations: one with an intake sump (referred to as the intake system) and another without an intake sump (referred to as the pump system), where the intake sump introduces non-uniform inflow conditions. First, under low flow conditions, typical unstable flow phenomena are observed in the impeller, including leading edge spillage and tip leakage vortex, which are consistent with previous research findings. Second, the analysis reveals that the non-uniform inflow causes the pump system to enter the hump zone earlier, as indicated by the external characteristic curves. Energy loss analysis identifies the increased energy loss at the bell mouth due to backflow from the impeller as the main contributor to the head drop. Finally, it is observed that submerged vortices exist at the bottom of the intake sump; however, their swirling strength is insufficient to significantly affect the hump characteristics of the intake system under low flow conditions. The distinguishing factor between the two systems is the distribution of axial velocity along the radial direction in the bell mouth. The higher axial velocity near the casing of the bell mouth in the pump system supplements the energy of the liquid near the shroud side of the impeller, thus delaying the occurrence of backflow.

Guide vane angle and reactor coolant pump performance during idling

In order to study the influence of different guide vane angle variation on performance characteristics of reactor coolant pump (RCP) during idling process, the external characteristics of RCP model with five different guide vane angles at idling process state were analyzed. Radial force characteristics and blade load characteristics of RCP were analyzed. The results show that the head and torque changes of pump with different guide vane angles in different idle period are consistent. The head of DY1model (Guide vane angle increases sharply first and then decreases gently, which convexity is large) is the highest and torque is small. The head drop rate of DY5 model (Guide vane decreases first and then increases, and the concavity is large) is the highest and torque is the largest. With the idling, the radial force of impeller and guide vane decreases gradually. The radial force of DY5 model impeller is small and the fluctuation range is weak. The radial force of DY4 model (Guide vane shows concavity change with gentle increase) impeller before idling is the largest. In the nonlinear transition of idle period, the total radial force of DY4 model is 235 N when idling for 32 s, which is nearly 30 times lower than that before idling, and the radial force decreases the most. In different idling periods, the radial force amplitude of guide vane of DY5 model is the largest, and the radial force decrease amplitude of guide vane of DY4 model is the largest in the whole idling period. The impeller blade load of DY4 and DY5 model pumps with concavity guide vane angle change law is significantly higher than that of other model pumps after the relative position of streamline is 0.6. When the relative position of the guide vane along the streamline direction is less than 0.5, the load fluctuation of the guide vane of each model pump is large. When the relative position is greater than 0.5, the blade load fluctuation is relatively small.

Design and experimental analysis of a new vertical ultra-low-head hydro turbine with the variation of outlet flow level on the head drop section of an open canal

Hydropower generation from ultra-low-head water resources is the salient category. The power can be tapped through different non-conventional turbines and is developing these days with different features. This research aims to develop a technology that applies to ultra-low-head resources from conceptualization to laboratory testing. Among several ultra-low-head water resources, it is concentrated on the power generation from the head drop section of the open canal flow through a new hydro turbine. A vertical shaft turbine with an axial flow type of runner having fixed, flat, and constant blade thickness including fixed guide vanes has been designed conventionally for 0.5 m of head and 0.088 m3/s of discharge. Several experiments have been conducted with fixing the level of flow outlet control from 0.0 m to 0.5 m creating the runner from free to submerged conditions is the novelty of this research. The results obtained for all the independent and dependent variables are presented and discussed for a constant flow of 0.088 m3/s and constant speed of 115 rpm conditions. The uncertainty on measurement was found ±1.85 % and the overall maximum efficiency obtained was 53.8 % for flow 10 % above the design flow. The research has concluded the use of outlet flow control is necessary to achieve the maximum efficiency of the turbine at a specific height and the overall efficiency can be advanced further through the optimization of blade profile.

Non-traumatic complete cervical spine dislocation with severe fixed kyphosis: successful multidisciplinary approach to a challenging case

BackgroundTo our knowledge, there is no previous report in the literature of non-traumatic neglected complete cervical spine dislocation characterized by anterior spondyloptosis of C4, extreme head drop, and irreducible cervicothoracic kyphosis.Case presentationWe report the case of a 33-year-old Caucasian man with a 17-year history of severe immune polymyositis and regular physiotherapy who presented with severe non-reducible kyphosis of the cervicothoracic junction and progressive tetraparesia for several weeks after a physiotherapy session. Radiographs, computed tomography, and magnetic resonance imaging revealed a complete dislocation at the C4–C5 level, with C4 spondyloptosis, kyphotic angulation, spinal cord compression, and severe myelopathy. Due to recent worsening of neurological symptoms, an invasive treatment strategy was indicated. The patient’s neurological status and spinal deformity greatly complicated the anesthetic and surgical management, which was planned after extensive multidisciplinary discussion and relied on close collaboration between the orthopedic surgeon and the anesthetist. Regarding anesthesia, difficult airway access was expected due to severe cervical angulation, limited mouth opening, and thyromental distance, with high risk of difficult ventilation and intubation. Patient management was further complicated by a theoretical risk of neurogenic shock, motor and sensory deterioration, instability due to position changes during surgery, and postoperative respiratory failure. Regarding surgery, a multistage approach was carefully planned. After a failed attempt at closed reduction, a three-stage surgical procedure was performed to reduce displacement and stabilize the spine, resulting in correct spinal realignment and fixation. Progressive complete neurological recovery was observed.ConclusionThis case illustrates the successful management of a critical situation based on a multidisciplinary collaboration involving radiologists, anesthesiologists, and spine surgeons.

Research on the centre-of-mass adjustment method for the head of an anthropometric test device based on a head impact biomechanics model

Head injury is the primary cause of serious lesions or death in automobile accidents. During crash tests, the mass and centre-of-mass position of the head of anthropometric test devices are crucial factors determining the accuracy of head injury test data. However, owing to the irregular shape as well as complex structure and material composition of the head of dummies, problems such as uneven mass distribution easily occur, resulting in deviations between the actual and designed positions of the centre-of-mass of the head. This study conducted research on head impact biomechanics and the centre-of-mass adjustment method for the head of dummies. Specifically, the biomimetic mechanical equivalent of the head was investigated, and head impact mechanics were analysed. Then, a predictive model was established for head drop mechanical response; the accuracy of this model was verified through head drop experiments. Based on the model, the law of centre-of-mass influence on the mechanical response of the dummy head was investigated, yielding an evaluation method for the different mechanical responses of the head. Using the rotational centre-of-mass measurement method, the mass and centre-of-mass position of the head were obtained. The distributed centre-of-mass adjustment method based on the principle of torque equilibrium was utilized to solve the deviations in the centre-of-mass position, the geometric dimensions of the counterweights and the centre-of-mass itself. Two counterweights were distributed on both sides of the internal cavity wall of the dummy head, resolving the positioning issue of the counterweights in the head cavity. The rationality of the centre-of-mass adjustment results was analysed using the predictive model for head impact mechanical response. The analysis results indicate that the centre-of-mass-adjusted dummy head better aligned with the mechanical response of the head in real collision scenarios, providing a new approach for the adjustment of the centre-of-mass of the head of dummies.

Dyspnea (breathlessness) in amyotrophic lateral sclerosis/motor neuron disease: prevalence, progression, severity, and correlates

Objective Dyspnea, or breathlessness, is an important symptom in amyotrophic lateral sclerosis/motor neuron disease (ALS/MND). We examined the measurement properties of the Dyspnea-12. Methods Rasch analysis enabled conversion of raw Dyspnea-12 scores to interval level metric equivalents. Converted data were used to perform trajectory modeling; those following different trajectories were compared for demographic, clinical, symptom, and functioning characteristics. Logistic regression examined differences between distinct trajectories. Results In 1022 people, at baseline, mean metric Dyspnea-12 was 7.6 (SD 9.3). 49.8% had dyspnea, severe in 12.6%. Trajectory analysis over 28 months revealed three breathlessness trajectories: group 1 reported none at baseline/follow-up (42.7%); group 2 significantly increased over time (9.4%); group 3 had a much higher level at baseline which rose over follow-up (47.9%). Group 3 had worse outcomes on all symptoms, functioning and quality of life; compared to group 1, their odds of: respiratory onset sixfold greater; King’s stage ≥3 2.9 greater; increased odds of being bothered by choking, head drop, fasciculations, and muscle cramps; fatigue and anxiety also elevated (p < .01). Conclusion Dyspnea is a cardinal symptom in ALS/MND and can be quickly measured using the Dyspnea-12. Raw scores can easily be converted to interval level measurement, for valid change scores and trajectory modeling. Dyspnea trajectories reveal different patterns, showing that clinical services must provide monitoring which is customized to individual patient need. Almost half of this large population had worsening dyspnea, confirming the importance of respiratory monitoring and interventions being integrated into routine ALS care.

Effect and mechanism of erosion in Pelton turbine and case studies—A review

Pelton turbines are widely used in hydropower stations located in mountainous regions, especially with water head drop of more than 2000 m. Due to the complex structure and working principle of the turbine, the flow is more complicated than reaction turbines, making the numerical simulation more difficult. The impulse action causes the occurrence of erosion phenomena in Pelton turbines, which will directly decrease the hydraulic efficiency and reduce the turbine's life. For investigating the erosion characteristics, computational fluid dynamics is widely used on variegated platforms according to their unique advantage. Thus, different platforms are introduced and compared in solving the multi-phase flow using a discrete element method or the other meshless methods. In addition, the erosion mechanism is studied and classified in different aspects such as impact angle and impact velocity. However, unlike the feasibility of numerical simulations, experimental work on the erosion mechanism is still challenging to reproduce. Furthermore, the state of experimental research is discussed by listing the various major facilities in operation and comparing their methods of experimental analysis. Case studies all over the world provide a very rich database of erosion patterns which would be highly useful in validation and verification of simulation and experimental results. Studies have shown that particle parameters, such as size, concentration, shape, velocity, and the interaction between particles and material surfaces, significantly impact the erosion of Pelton turbines. In response to this erosion, upgrading materials and implementing geometric optimization have proven to be effective strategies.

Dropped head syndrome in anti‐MuSK antibody‐positive myasthenia gravis with possible concurrent axial myopathy

AbstractBackgroundDropped head syndrome (DHS) is a group of disorders that result in anterior neck flexion. Myasthenia gravis (MG) is a common cause of DHS. Previous reports have suggested that concurrent myopathy involving the paraspinal musculature may underlie DHS in patients with anti‐acetylcholine receptor antibody‐positive or thymoma‐associated MG.Case PresentationA 64‐year‐old woman presented with a 3‐month history of head drop and lordosis. Neurological examination revealed bilateral ptosis and weakness of the posterior neck extensors. Electrophysiology suggested neuromuscular junction involvement. Serum anti‐MuSK antibodies were positive, and generalized anti‐MuSK antibody‐positive myasthenia gravis (MuSK‐MG) was diagnosed. Needle electromyography (nEMG) of the splenius capitus and paraspinal muscles revealed acute and chronic myogenic changes. Imaging suggested paraspinal muscle atrophy. nEMG and magnetic resonance imaging (MRI) of both extremities were normal, and autoimmune myopathy‐related antibody testing was negative.ConclusionThymoma‐negative MuSK‐MG, demonstrating treatment‐refractory DHS, may present with concurrent axial myopathy.

Experimental study on multiple characteristics of multi-source AE signals during cavitation process of waterjet propulsion pump

In order to investigate the cavitation-induce acoustic emission (AE) characteristics of a waterjet propulsion pump, a synchronous experimental system consisting of a test pump, a high-speed camera, and acoustic emission sensors has been established. The characteristic parameters of AE signals are extracted to established the quantitative relationships between cavitation status and AE signals. These characteristic parameters mainly consist of the ringing count rate Rc , energy release rate Er , and Hurst index Hi . The cavitation status of the test pump is reflected in the characteristic parameters of the AE signals obtained by the sensors installed at different locations. The incipient blade suction side (SS) cavitation as well as the blade tip gap cavitation can be detected through the change of characteristic parameters of AE signals at impeller inlet. The start of head drop can be reflected by the variety of characteristic parameters of AE signals at impeller middle. Large-scale cavitation will lead to the breakdown of pump performance and dramatically characteristic parameters’ change of AE signals can be measured by the sensors located at impeller outlet.

A child with Epileptic and nonepileptic Head Drops

A child with Epileptic and nonepileptic Head Drops

Evaluating the Efficacy of the Zelisken Ball in Shortening the First Stage of Labor: A Quasi-Experimental Study

During labor, mothers frequently report having excruciating contractions that continue for hours or even days. An assistive gadget is required to expedite labor and aid in the baby's head drop. The Zelisken Ball, an invention of the research group, is a bolster-shaped ball used in basic exercises or physical care. The study aimed to determine whether using the Zelisken Ball could shorten the time pregnant mothers spend in the first stage of labor. Pregnant women's level of comfort and satisfaction while using it, along with its effects on each delivery stage, were highlighted. Using a control group, the study used a quantitative methodology and a quasi-experimental post-test-only design. Purposive sampling was employed to identify 50 postpartum patients for the sample. The Zelisken Ball was utilized by the intervention group in this study, while the Peanut Ball was used by the control group. Questionnaires were used to gather data, and SPSS software was implemented to perform an Independent Sample t-test to determine differences between the two groups. The mothers who utilized the Zelisken Ball advanced through the first stage of labor more quickly, according to the data, with a difference of 1.29 hours (77.4 minutes) between them and the control group (8.3 hours) who used the Peanut Ball. The results of the data analysis indicate that mothers who used the Zelisken Ball and those who utilized the Peanut Ball had significantly different first-stage labor durations (p-value of 0.026, &lt;0.05). As a result, the Zelisken Ball shows great promise as a useful tool for accelerating the early stage of labor. The research has been modified to create Zelisken, which is two-thirds the size of a peanut ball and has an indentation of ½ on the ball. The outer material of Zelisken is made of Oscar fabric, and the inside is filled with foam, whereas the peanut ball is made of PVC and has an interior filled with air. Future research, however, needs to increase the sample size to include a wider range of respondents to strengthen the findings' generalizability.

Botulism Presented with Clinical Head Drop, Approach to Botulinum Toxin A: A Case Report

Botulism Presented with Clinical Head Drop, Approach to Botulinum Toxin A: A Case Report

Evaluating the Longitudinal Connectivity of Dorim Stream in Seoul based on Artificial Constructure and Fish Data

The vertical connectivity of the river aquatic ecosystem was evaluated based on fish and artificial structures in Dorim stream, an urban stream in Seoul. As a result of a survey in the downstream area in 100.0 m of a total of 71 artificial structures, 13,728 individuals of fishes belonging to five orders, seven families, and 25 species were investigated, with the dominant species Zacco platypus and the subdominant species Rhynchocypris oxycephalus. As for endemic species, seven species were investigated and in terms of feeding characteristics, omnivorous species were the most common with 17 species (68%). Also an alien species, Poecilia reticulata was found. Fish species tended to decrease as the survey was conducted to upstream. Based on the movement characteristics of the fish species and the features of artificial structure survey results, the longitudinal continuity of each artificial structure was evaluated as 43 continuity, two damaged, 19 discontinuity, and seven absent. In inclined structures, stream velocity was found to be the main factor for discontinuity. In vertical structures, the down depth and head drop appeared to be the main factors for discontinuity. The results of this survey are expected to serve as basic data for the conservation of river aquatic ecosystems in the future.

Design and Experiment of Grain Lifter for Sorghum Harvester

In order to solve the problems of grain lifter in sorghum harvesting, such as ear loss and serious crop leakage loss, combined with the physical and mechanical characteristics of sorghum, the segmented and reverse spiral grain lifter for sorghum harvesting and cutting table was developed, and the design method of the main structural parameters of the grain lifter was determined. The comparative test of the working effect of the clasp showed that the working effect of the cutting table with the clasp was better than that without the clasp, which effectively reduced the harvest loss of the cutting table. By using Box–Behnken experimental design method, the influence law of forward speed, tilt angle, and rotation speed of grain lifter on the rate of ear loss and harvest loss in sorghum harvesting was investigated. The regression mathematical model and response surface of the rate of ear loss and harvest loss and analysis factors were established, and the optimal working parameters of the grain lifter were determined. The forward speed was 0.8 m/s, the tilt angle of the grain lifter was 28°, and the rotation speed of the grain lifter was 330 r/min. Under these conditions, the spike loss rate was 2.01, the leakage loss rate was 2.19, and the error with the theoretical value was less than 3%, which proved the rationality of the optimized combination parameters. In the harvest of crooked and fallen sorghum, the grain lifter can effectively reduce the loss of sorghum head drop and lodging leakage, ensure the reliability of the cutting table, and achieve low loss and efficient harvest of sorghum.

Experimental comparison of the upstream head using the non-rotating model of the vertical ultra-low head hydro turbine with its prototype

A vertical ultra-low head (VULH) turbine is a pico-scale hydro turbine applicable to open canal flow with or without head drop. This conceptualized turbine rotates at a lower speed. In the case of water flow on a canal without head drop condition, the prediction of the upstream head is challenging due to the change in the direction of the water flow path on this conceptualized system. Assuming the head at the primary level of design, an experimental study has been conducted to judge the upstream head of water flow using the two-dimensional non-rotating model (NRM) before the use of a prototype of the turbine. The runner was designed with a conventional method whereas the design of NRM was based on the diameters of the runner designed and the orifice openings on it. The experiments were conducted on a newly developed VULH Turbine test rig of size 10 m x 1.5 m x 2 m with a maximum flow rate capacity of 120 LPS and a maximum upstream head of 0.75 m. The tests were completed for upstream head variation using three different sets of NRM having an orifice cut angle of 15°, 18°, and 22.5° and a prototype of the runner at a constant speed for different flow rates. From the comparisons made, the closest NRM was selected that showed a similar upstream head at the maximum efficiency point of the runner. The research concluded with the finding that the NRM can be used to predict the upstream head of the VULH turbine instead of the rotating model.

Three-Dimensional Flow Simulation by a Hybrid Two-Phase Solver for the Assessment of Liquid/Gas Transport in a Volute-Type Centrifugal Pump with Twisted Blades

A hybrid two-phase flow solver is proposed, based on an Euler–Euler two-fluid model with continuous blending of a Volume-of-Fluid method when phase interfaces of coherent gas pockets are to be resolved. In a preceding study on a two-dimensional bladed research pump with reduced rotational speed, the transition from bubbly flow to coherent steady gas pockets observed in optical experiments with liquid/gas flow could be well captured by the hybrid solver. In the present study, the experiments and solver validation are extended to an industrial-scale centrifugal pump with twisted three-dimensional blades and elevated design rotational speed. The solver is combined with a population balance model, and a scale-adaptive turbulence model is employed. Compared to the two-dimensional bladed pump, the transition from agglomerated bubbles flow to attached gas pockets is shifted to larger gas loading, which is well captured by the simulation. The pump head drop with increasing gas load is also reproduced, showing the hybrid solver’s validity for realistic pump operation conditions.

HYPER: Computer-Assisted Optimal Pump-as-Turbine (PAT) Selection for Microhydropower Generation and Pressure Regulation in a Water Distribution Network (WDN)

Although pressure reducing valves (PRVs) have traditionally been employed to regulate pressure and reducer water leakage, researchers have been increasingly investigating the strategy of micro-hydropower generation using pumps as turbines (PATs) to enable both pressure reduction and energy production as an alternative strategy in water distribution networks (WDNs). However, due to the continuous variability of flow discharge during the day, selecting the optimal PAT remains a challenging issue. To address this, the authors have developed HYPER, a freely available software app that implements an innovative approach for selecting the most suitable PAT in systems that involve both hydraulic and/or electrical regulation. In enabling the identification of the PAT parameters that maximize energy production, HYPER thus provides a fast and effective PAT selection tool. The effectiveness of the proposed approach was further demonstrated with application to a real WDN. Four operational patterns varying in terms of available flow and head drop were considered, showing that the most efficient pumps consistently tended to be located in close proximity to the maximum produced energy. Furthermore, the results confirmed that hydraulic regulation and coupled hydraulic/electric regulation-based installation layouts represent the best solutions in terms of energy produced. The solely electrical regulation option, given its poor flexibility, returns in all cases lower energy production with the lower adaptability of commercial pumps.