Circulation Rate Research Articles

Natural circulation oscillation in a seawater loop during startup

Aiming to improve nuclear safety by using seawater as an alternative emergency coolant during an accident, the knowledge of two-phase flow instabilities and heat transfer performances of seawater is needed. Startup experiments from the quiescent state at room temperature of 20–23 °C are carried out by raising heating power with 3.5 wt% artificial seawater in a natural circulation loop. De-ionized water is adopted as well for the comparative study. In this paper, a type of natural circulation oscillation at the modified heat fluxes of 383.70–530.62 kW/m2 and 404.05–594.97 kW/m2, respectively, for seawater and de-ionized water, with intermittent inlet mass flow rates is exclusively investigated, as a part of the experimental studies of two-phase flow instabilities during the startup of a natural circulation loop. Visualizations of two-phase flow behaviors at the power of 2206 W in seawater reveal the unique bubble foam regimes at the outlet of the heated section, tiny bubbles at the inlet of the riser, and the possible elongated slug bubbles at the central region of the riser.The natural circulation oscillations for two fluids are characterized by four distinct stages in sequence: calm state (stage 1), accumulations of foam/slug bubbles in seawater/de-ionized water (stage 2), propagations of foam/slug bubbles in seawater/de-ionized water (stage 3), and restorations (stage 4). The same period for stages 1, 3, and 4 for both fluids are 25 s, 4 s, and 5 s, respectively. For stage 2, the period measured as 12.5 s in seawater is significantly shorter than that recorded as 45 s in de-ionized water, leading to earlier systematic natural circulation rates. It is possibly caused by the much stronger accumulation effect of tiny bubbles in the riser, resulting in vast buoyant forces by draining more liquid out of the riser. The intermittent peak inlet mass flow rates of 0.017 kg/s and 0.023 kg/s are recorded, respectively, for seawater and de-ionized water. It would not induce a pressure drop increase over the riser while cause a very high pressure drop oscillation of 4.67 kPa in de-ionized water. Slower circulation rates induce smaller wall temperature drops of 3.6 °C in seawater than that of 5.2 °C in de-ionized water. Under zero flow rate conditions, the wall temperatures are mainly kept at 117–119 °C, accompanied by bubble foam without ruptures in seawater, while that are about 115 °C with slug bubbles due to bubble coalescences in de-ionized water. It demonstrates that the immobile foam may deteriorate the heat transfer under pool-like conditions.

Study on the Impact of Offshore Wind Farms on Surrounding Water Environment in the Yangtze Estuary Based on Remote Sensing

Offshore wind farms (OWFs), built extensively in recent years, induce changes in the surrounding water environment. The changes in the suspended sediment concentration (SSC) and chlorophyll-a concentration (Chl-aC) induced by an OWF in the Yangtze River Estuary were analyzed based on Chinese Gaofen (GF) satellite data. The results show the following: (1) The flow near the wind turbines makes the bottom water surge, driving the sediment to “re-suspend” and be lost, deepening the scour pit around the bottom of the wind turbines, which is known as “self-digging”. The interaction between the pillar of a wind turbine and tidal currents makes hydrodynamic factors more complicated. Blocking by wind turbines promoting the scour of the bottom seabed of the OWF results in speeding up the circulation rate of sediment loss and “re-suspension”, which contributes to the change in the SSC and Chl-aC. This kind of change in sediment transport in estuarine areas due to human construction affects the balance of the ecological environment. Long-term sediment loss around wind turbines also influences the safety of wind turbines. (2) The SSC and Chl-aC are mainly in the range of 200–600 mg/L and 3–7 μg/L, respectively, in the OWF area, higher than the values obtained in surrounding waters. The SSC and Chl-aC downstream of the OWF are higher than those upstream, with differences of 100–300 mg/L and 0.5–2 μg/L. High SSC and Chl-aC “tails” appear downstream of wind turbines, consistent with the direction of local tidal currents, with lengths in the range of 2–4 km. In addition, the water environment in the vicinity of a wind turbine array, with a roughly 2–5 km scope (within 4 km during flooding and around 2.5 km during ebbing approximately) downstream of the wind turbine array, is impacted by the OWF. (3) In order to solve the problem of “self-digging” induced by OWFs, it is suggested that the distance between two wind turbines should be controlled within 2–3.5 km in the main flow direction, promising that the second row of wind turbines will be placed on the suspended sediment deposition belt induced by the first row. In this way, the problems of ecosystem imbalance and tidal current structure change caused by sediment loss because of local scouring can be reduced. Furthermore, mutual compensation between wind turbines can solve the “self-digging” problem to a certain extent and ensure the safety of OWFs.

Monitoring, modeling, and optimization of parameters affecting the recovery efficiency of acid gases from a sweetening unit

Amine processes are the advanced technology available today for the removal of carbon dioxide (CO2) and hydrogen sulfide (H2S) acid gases. Methyldiethanolamine (MDEA) is a well-known tertiary amine used selectively for the removal of carbon dioxide from natural gas. There are many parameters that can affect the efficiency of separating these acid gases from natural gas. In this paper, we have studied, modeled, and optimized different operating parameters of sour gas feed and MDEA solution which affect the CO2 recovery efficiency from an existing sweetening unit. These operating parameters are the sour gas feed temperature and pressure, volume ratio (%) of carbon dioxide in the feed gas, amine inlet temperature, and amine circulation rate. Actual data were collected from an industrial CO2 sweetening unit over one year. These data were used to study the effect of the studied operating parameters on the recovery efficiency of CO2 from the sweetening unit. All studied operating parameters were found to have an impact on the recovery efficiency of the removed gases. A response surface methodology approach was used in Design-Expert software version 13 to model the relationship between considered operating parameters and CO2 recovery efficiency. In addition, Design Expert numerical optimization has been used to maximize CO2 recovery efficiency. The results showed that the optimal range of sour gas feed temperature is 34.71 to 45.56 °C, sour gas feed pressure is 8.32 to 10.04 barg, the volume ratio (%) of carbon dioxide in the sour gas feed is 8.51 to 10.15, the temperature of the amine is 38.03 to 43.96 °C, and the amine circulation rate is 788.39 to 1122.35 m3/h. The presented work can be considered as a guideline for increasing the recovery efficiency of CO2 for both new and existing sweetening units.

Photocatalytic Performance and Degradation Pathways of Z‐Scheme BiO2−X−Ag3PO4 Photocatalysts with Oxygen‐Deficient Structures

AbstractIt is a practical way to raise the efficiency of photocatalysis by using oxygen vacancy defect modified materials. In this experiment, a Z‐scheme BOA composite photocatalyst with defect structure was prepared by hydrothermal in situ precipitation method. The optimal ratio of 1.5 BOA showed excellent photocatalytic degradation performance for MO, TC and CIP under visible light irradiation, and maintained good structural stability and circulation rate after five cycles. The increased photocatalytic activity of the composite can be explained to the heterojunction interface‘s synergistic effects and the quicker electron hole transit rate caused by the surface oxygen vacancy defect. XPS and EPR confirmed the existence of anoxic structure in the composite, PL and photocurrent confirmed the high electron hole transfer rate. The active species that contributed to the degradation process were validated by the active species capture experiment and ESR. LC–MS speculated the possible degradation path of CIP. Finally speculated the reaction mechanism of Z‐scheme BOA composite photocatalyst. Using the anoxic structure of BiO2−X to form a Z‐scheme heterostructure with Ag3PO4, the oxygen vacancy as the electron capture center and active site is conducive to improving the photogenerated electron transfer rate, thereby improving the structural stability and photocatalytic performance of the complex.

Methylene blue as an adjuvant during cardiopulmonary resuscitation: an experimental study in rats

IntroductionMethylene Blue (MB) has been shown to attenuate oxidative, inflammatory, myocardial, and neurological lesions during ischemia-reperfusion and has great potential during cardiac arrest. This study aimed to determine the effects of MB combined with epinephrine during cardiac arrest on myocardial and cerebral lesions. MethodThirty-eight male Wistar rats were randomly assigned to four groups: the sham group (SH, n = 5), and three groups subjected to cardiac arrest (n = 11/group) and treated with EPI 20 µg.kg−1 (EPI), EPI 20 µg.kg−1 + MB 2 mg.kg−1 (EPI + MB), or saline 0.9% 0.2 ml (CTL). Ventricular fibrillation was induced by direct electrical stimulation in the right ventricle for 3 minutes, and anoxia was maintained for 5 minutes. Cardiopulmonary Resuscitation (CPR) consisted of medications, ventilation, chest compressions, and defibrillation. After returning to spontaneous circulation, animals were observed for four hours. Blood gas, troponin, oxidative stress, histology, and TUNEL staining measurements were analyzed. Groups were compared using generalized estimating equations. ResultsNo differences in the Returning of Spontaneous Circulation (ROSC) rate were observed among the groups (EPI: 63%, EPI + MB: 45%, CTL: 40%, p = 0.672). The mean arterial pressure immediately after ROSC was higher in the EPI+MB group than in the CTRL group (CTL: 30.5 [5.8], EPI: 63 [25.5], EPI+MB: 123 [31] mmHg, p = 0.007). Serum troponin levels were high in the CTL group (CTL: 130.1 [333.8], EPI: 3.70 [36.0], EPI + MB: 43.7 [116.31] ng/mL, p < 0.05). ConclusionThe coadministration of MB and epinephrine failed to yield enhancements in cardiac or brain lesions in a rodent model of cardiac arrest.

Experimental investigation of three-dimensional gas-solid flow in CFB cyclone separator using electrical capacitance volume tomography

The anisotropic three-dimensional flow field inside cyclone separators makes it challenging to capture the gas-solid flow characteristics, and the internal behavior of the cyclone separator remains not fully understood. The gas-solid flow characteristics inside a cyclone separator of the circulating fluidized bed (CFB) are investigated using electrical capacitance volume tomography (ECVT). The solid fraction, average velocity, and frequency characteristics of particles were extracted from ECVT images. The experimental results show that the number of turns for the dust strands spirals gradually increases as the inlet gas velocity Uf increases. The axial velocity of the particles in the cylindrical part of the cyclone separator is always greater than in the conical part. In addition, the difference in inlet gas velocity and particle size results in different particle flow characteristics in the CFB riser. It leads to the differences in the particle circulation rate and flow pattern in the cyclone separator.

New formulations and experimental validation of non-stationary convolutions for the fast simulation of time-variant flowrates in ground heat exchangers

Flowrate control can have a significant positive impact on the thermal performance and economic profitability of ground-source heat pump systems. Including dynamic advective processes in the design phase, however, remains a challenging task, as few computationally efficient modeling tools allow for their adequate and accurate representation. The present work addresses this issue by presenting new formulations of non-stationary convolutions, an efficient simulation algorithm that relies on the theory of linear time-variant systems for predicting the thermal response of a ground heat exchanger to both dynamic heat loads and flow rates. First, the new original formulations are presented, which include (1) a simple time-domain expression and (2) a fast frequency-domain expression. Then, the efficiency and validity of the new formulations are verified using experimental multi-flowrate thermal response tests involving dynamic circulation, pumping and bleed flow rates in closed-loop and standing column well ground heat exchangers. Results show that the new formulations can reproduce the outlet fluid temperature of both experimental test cases with good accuracy ( MAE = 0.06 ∘ C and 0.26 ∘ C , respectively). At last, the high efficiency of the new frequency-domain expression is demonstrated, with the computing times ( 0.04 s and 0.01 s ) being 100 and 8 times faster than the original formulation in both scenarios.

Mineral Scaling Impact on Petrophysical Properties of Reservoir Rock in a Geothermal Field Located in Northwestern Iran

Summary As the usage of geothermal energy as a zero-emission power resource continues to grow in significance, comprehending the interplay between physical and chemical processes within geothermal reservoirs becomes crucial. In this study, a computationally efficient fluid flow and heat transfer model, combined with a fluid chemistry model, is used to simulate fluid circulation and mineral precipitation in reservoir rock, resulting in changes in rock porosity and permeability. A 2D hybrid approach is employed to solve transient mass and momentum conservation equations, coupled with an analytical solution of the energy equation proposed in the literature for geological formations. A marching algorithm is utilized to calculate velocity and temperature fields in the axial direction within the production zone. Mineral scaling is addressed using the outputs of the hybrid model to perform saturation index (SI) and solution/dissolution computations for qualitative and quantitative mineral precipitation modeling. Multiple criteria are considered to assess the likelihood and intensity of fouling issues. The analysis results are used in an empirical model to estimate rock secondary porosity and permeability changes over a 5-year period of heat extraction. The developed simulator is applied to model a site in the Sabalan geothermal field in Iran, and its initial verification is conducted using data from the same site in the literature. The findings in the study for a sensitivity on fluid circulation rate reveal that increasing water circulation flow rate increases precipitation rate and pumping power required. Furthermore, even minor instances of pore blockage can result in notable reductions in permeability. Consequently, ensuring precise control over pressure and temperature during the production phase becomes progressively crucial for both reservoir integrity and production assurance. The proposed framework provides a promising approach for accurate and efficient simulation of geothermal reservoirs to optimize power generation and minimize environmental impact.

PWR natural circulation at a small break LOCA

In this paper, a one-dimensional quasi-steady model has been developed to analyse the potential impacts of reduced primary coolant inventory on natural circulation. This model focuses on the development of expressions for the coolant inventory, temperature distributions, and mass flow rate. The model encompasses a range of fluid flow scenarios, including single-phase, combined single-and-two-phase, and two-phase natural circulation, as well as the phenomenon of reflux condensation. The model is also utilized to examine the impact of reactor core power on natural circulation parameters. Comparisons with experimental findings and earlier research are made, highlighting a satisfactory level of agreement with the analytical findings. Based on the findings of this study, it has been observed that within the range of primary coolant inventory of 100–60% and core decay power of 1.5–5% of full power, natural circulation in a PWR type system has the potential to serve as an effective mechanism for transferring core decay heat to the secondary loop. The flow rates of natural circulation in pressurized water reactors (PWRs) are observed to have a significant dependence onthe amount ofliquid inventory, whereas their relationship with power level is comparatively less pronounced. The flow rate of a pressurized water reactor (PWR) system tends to exhibit its highest value within a specific range of inventory, typically falling between 60% and 80%. The transition between the different modes of natural circulation is observed to exhibit a smooth transition, with varying system inventories.

Preparation and Evaluation of Composite Hydrogel for Reducing the Leakage Rate of Lost Circulation.

Fractured reservoirs are widely distributed and rich in hydrocarbon resources. When encountering fractured reservoirs during the drilling process, it is often accompanied by formation losses characterized by high leak-off rates, causing severe damage to the reservoir and hindering the detection of oil and gas layers, which is not conducive to the accurate and efficient development of the reservoirs. Conventional plugging materials have poor retention effects in the fractures, resulting in the low stability of the sealing layer. The treatment of malignant lost circulation in fractured formations is an urgent problem to be solved in drilling engineering. This article focuses on improving the success rate of formation plugging through the combined use of multiple plugging materials and develops a composite hydrogel that can effectively reduce leakage rates. This hydrogel is mainly composed of materials such as polyvinyl alcohol, borax, and sodium silicate. It has good temperature resistance, maintains good gel strength at 60 °C, and can maintain long-term performance stability under simulated geological water conditions with salinity of 12,500 mg/L. For immersion corrosion by water or gasoline, the amount of corrosion is small and its fundamental performance remains largely unchanged. Through indoor simulation of a leak formation scenario, the hydrogel demonstrates commendable sealing pressure-bearing capacity. In terms of delaying fluid leakage, mixing the hydrogel with cement slurry at a ratio of 1:1 can delay the leakage rate of the cement slurry by a factor of 5.29.

Experimental Research on the Gas-Solid Flow Characteristics in Large-Scale Dual Fluidized Bed Reactor

A dual fluidized bed (DFB) reactor is the main operating system of various energy-efficient and clean utilization technologies. The gas-solid flow characteristics of the DFB reactor greatly affect the efficiency of various technologies. A large-scale DFB reactor with a maximum height of 21.6 m was built and relevant cold mode tests were carried out in this study. The effects of the superficial gas velocity of both beds, static bed height and particle size on the distribution of both pressure and solid suspension density, solid circulation rate, solid inventory distribution ratio and other characteristics were studied. For 282 μm-particles, the solid suspension density in the dense phase zone of the two beds was 100–400 and 400–800 kg/m3, respectively, when the static bed height was 0.65 m; the solid circulation rate was about 0.87–1.75, 1.04–3.04 and 1.13–3.69 kg/(m2s) when the static bed height was 0.65, 0.95 and 1.25 m, respectively. The solid circulation rate was positively correlated with the static bed height and the superficial gas velocity of both beds, yet negatively correlated with the particle size. Additionally, the empirical equation of solid circulation rate and the empirical equation of solid inventory distribution ratio were proposed, respectively. The material control method of the DFB reactor is put forward.

Studies of the Effect of the Shredder Design on the Material Circulation Rate in the Shredding Chamber and Its Unit Load

Studies of the Effect of the Shredder Design on the Material Circulation Rate in the Shredding Chamber and Its Unit Load

First serological evidence of MERS-CoV in dromedary camels from Algeria

Middle East Respiratory Syndrome (MERS) is a zoonotic disease. Dromedary camel is responsible of its transmission to humans. Accordingly, several human cases have been reported worldwide with a high mortality rate. In Algeria, no data reported on MERS prevalence in camels. This is a first seroprevalence study MERS-CoV in Algerian dromedaries. A total of 87 camel blood samples from EL -MENIAA and Ghardaia, were analyzed by anti-MERS-CoV IgG ELISA camel. The seroprevalence was 64 % and it significantly increases with age. Larger serological and molecular screening is needed to precisely determine the rate of MERS active circulation among Algerian dromedary population.

Multibubble Behavior and Solid Circulation Rate in a Gas–Liquid–Solid Circulating Microfluidized Bed

Multibubble Behavior and Solid Circulation Rate in a Gas–Liquid–Solid Circulating Microfluidized Bed

Parasympathetic Dominance Decreases the Choroidal Blood Flow Velocity Measured Using Laser Speckle Flowgraphy.

This study aimed to examine the changes to choroidal blood flow velocity using laser speckle flowgraphy (LSFG) in healthy eyes after warm water immersion at 40°C. Data regarding the right eyes of 23 healthy volunteers were included. The mean blur rate (MBR) of the macula, which represents the choroidal blood flow velocity, was evaluated using LSFG. Intraocular pressure (IOP), systolic blood pressure (SBP), diastolic blood pressure (DBP), mean blood pressure (MBP), ocular perfusion pressure (OPP), and MBR were assessed at baseline, immediately after immersion (0 minutes), and 10, 20, and 30 minutes later. At 0 minutes, SBP, DBP, MBP, and OPP values were lower than those at baseline. The MBR significantly declined immediately after immersion to -6.0 ± 5.2%. However, there were no changes in these parameters after 10, 20, or 30 minutes. A significant positive correlation was observed between the MBR, SBP, DBP, MBP, and OPP values. In healthy individuals, the dominant parasympathetic activity induced by warm stimulation reduced the choroidal hemodynamic rate in the macula and decreased systemic circulatory dynamics, which normalized after 10 minutes. These findings suggest that the dominant parasympathetic activity induced by warm water immersion at 40°C may lead to a reduction in the systemic circulation rate and choroidal blood flow rate in the macula. These findings may help prevent and treat various retinal choroidal diseases, in which sympathetic hyperactivity is involved in the pathogenesis of the disease.

Evaluating the contribution of climate change and urbanization to the reversal in maximum surface wind speed decline: Case study in the Yangtze River Economic Belt, China

The drivers of variations in wind extremes, such as maximum surface wind speed (MSWS), are important considerations in long-term wind speed studies in urbanized regions, and the contribution of changed surface roughness has been well-examined. However, the contribution of other drivers of the variation in MSWS, including atmospheric circulation and increasing surface air temperature, remains largely unknown. This study integrated statistical methods, spatial mapping techniques, meteorological station data, and land use products to investigate the spatiotemporal influence and integrated contribution rates of surface air temperature, surface roughness, and atmospheric circulation on MSWS in the Yangtze River Economic Belt, China. The annual mean MSWS decreased (−0.662 m·s−1·10a−1) during 1973–2011 and increased (0.115 m·s−1·10a−1) during 2011–2020, whereas the seasonal changes differed significantly, with changes in the mean MSWS in winter being greater than in the other seasons. Moreover, increases in surface air temperature owing to surface roughness change, as well as atmospheric circulation (annual total explanatory power: 91.2%) contributed to MSWS changes from 1973 to 2020. The explanatory power of the integrated contribution was clearly influenced by urbanization, especially at the high urbanization level in the warm season (>86%), and the influence of atmospheric circulation was higher than that of urbanization in the cold seasons at the moderate level (>83%), implying that atmospheric circulation partially affected the key role of urbanization in the reversal of MSWS. The analysis framework of this study, which is based on the contribution rates of surface air temperature, surface roughness, and atmospheric circulation, is transferable to other cities and can be utilized to assist in both decreasing the risk of urban wind extremes and improving wind resource utilization.

Changes in vital signs during adrenaline administration for hemostasis in intracordal injection: an observational study with a hypothetical design of endotracheal adrenaline administration in cardiopulmonary arrest

BackgroundThe background is that intravenous adrenaline administration is recommended for advanced cardiovascular life support in adults and endotracheal administration is given low priority. The reason is that the optimal dose of adrenaline in endotracheal administration is unknown, and it is ethically difficult to design studies of endotracheal adrenaline administration with non-cardiopulmonary arrest. We otolaryngologists think so because we administered adrenaline to the vocal folds for hemostasis after intracordal injection under local anesthesia, but have had few cases of vital changes. We hypothesized that examining vital signs before and after adrenaline administration for hemostasis would help determine the optimal dose of endotracheal adrenaline.MethodsWe retrospectively examined the medical records of 79 patients who visited our hospital from January 2018 to December 2020 and received adrenaline in the vocal folds and trachea for hemostasis by intracordal injection under local anesthesia to investigate changes in heart rate and systolic blood pressure before and after the injection.ResultsThe mean heart rates before and after injection were 83.96 ± 18.51 (standard deviation) beats per minute (bpm) and 81.50 ± 15.38 (standard deviation) bpm, respectively. The mean systolic blood pressure before and after the injection were 138.13 ± 25.33 (standard deviation) mmHg and 135.72 ± 22.19 (standard deviation) mmHg, respectively. Heart rate and systolic blood pressure had P-values of 0.136, and 0.450, respectively, indicating no significant differences.ConclusionsAlthough this study was an observational, changes in vital signs were investigated assuming endotracheal adrenaline administration. The current recommended dose of adrenaline in endotracheal administration with cardiopulmonary arrest may not be effective. In some cases of cardiopulmonary arrest, intravenous and intraosseous routes of adrenaline administration may be difficult and the opportunity for resuscitation may be missed. Therefore, it is desirable to have many options for adrenaline administration. Therefore, if the optimal dose and efficacy of endotracheal adrenaline administration can be clarified, early adrenaline administration will be possible, which will improve return of spontaneous circulation (ROSC) and survival discharge rates.

Optimization of low-NOx Burner Under the Combined Influence of Multiple Factors

ABSTRACT The influence degree of structural parameters and operating parameters on the low NOx performance of burners was studied by numerical simulation and orthogonal experiment. Excess air coefficient (factor A) and flue gas circulation rate (factor B) were used as operating factors, fuel nozzle diameter (factor C), cyclone blade end deflection angle (factor D), flame-stabilizer inclination angle (factor E), and internal circulation tube diameter (factor F) were used as structural factors, the average temperature (T av), maximum temperature (T max) of the combustion chamber, and NO emission value at the combustion chamber outlet (M NO) were used as indicators. Range analysis and variance analysis were used to analyze the specific influence of the above factors on the indicators. In the studied cases, the most significant factor affecting T av and M NO is the factor B, followed by the factor C. The more significant factor affecting T max is the factor A, followed by the factor C. The coupling of multiple parameters has a significant effect on the distribution of flow field in the combustion chamber. Vortices are produced in all the cases studied. The vortices are basically symmetrical, but the number of vortices varies from 2 to 6. The results show that the burner has good flame stability.

A PIV study to quantify the relationships between viscoelasticity and flow behavior in stirred tanks

Quantitative data on fluid dynamics in stirred tanks with viscoelastic fluids are scarcely available. Therefore, a particle image velocimetry study on flow phenomena occurring when agitating viscoelastic liquids with radial and axial impellers is presented. Different flow regimes exist, which result from interactions between elastic normal stresses and inertial forces: While for all agitators an axial pumping effect is found in the elastic regime, (semi-)radial flow patterns result in inertia-dominated flows. In the transition regime, locally limited zones exist dominated by either elasticity or inertia. This leads to a flow compartmentalization, a related pseudo-stagnation flow and reduced circulation rates. Which of the flow regimes is present can be predicted by the use of the elasticity number. With it, circulation flow numbers and flow distributions are standardized: In elastic flow conditions, these are constant. Thus, a scaling of the log-normally distributed velocities to the tip speed in this regime is possible.

Pencegahan Penyalahgunaan Narkoba Perspektif Al-Qur’an (Kajian Tafsir Maudhu’i)

Drug abuse is a very heartbreaking and worrying problem and humanitarian issue. Drugs have infected all ages, from the lower class to the upper class, from children to the elderly, and from the uneducated to the educated, and even the victims continue to fall. This paper aims to reveal the Qur'anic efforts and find alternative solutions that will be able to reduce the rate of circulation and find ways to prevent drug abuse in the Qur'an. This paper, including the type of library research, uses a thematic approach (Tafsir Maudu'i). A method that directs the view of a particular theme and then seeks the view of the Qur'an on that theme by collecting, understanding, and analyzing verses that talk about the theme under study. The research results and findings from this study, among others, are: first, strengthening the foundation of religion; second, fostering the Qur'anic generation; third, growing noble character; fourth, providing advice in a civilized manner; fifth, calling on goodness and preventing evil; sixth, praying that all matters will be expanded; seventh, continuously in obedience; and eighth, hastening to give advice about religion. Furthermore, this research is still far from perfect. Further research is needed with a more varied and comprehensive approach. So that the prevention of drug abuse can be more controlled.