Fluid Diffusion Research Articles

Viscoelastic effects on the double-diffusive oscillatory flow in a fluid-saturated porous layer

The viscoelastic effects on the double diffusive oscillatory flow in a fluid-saturated porous layer are investigated. A modified Darcy–Oldroyd-B model is used to characterize the non-Newtonian fluid behavior flow in a porous layer. Analytic solutions of the dimensionless governing equations of fluid flow are obtained and the effects of the flow parameters on temperature, concentration, velocity profiles, skin friction and rate of heat transfer are discussed and shown graphically. It is interesting to note that skin friction increases on both channel plates as injection increases on the heated plate. Increase in the strain retardation parameter is to decrease the fluid velocity, while an opposite trend is noticed with increasing stress relaxation parameter. The study reiterates that the consideration of viscoelastic fluid is very important in proper considerate of oscillatory flow in double diffusive fluid systems.

Lamellar Wood Sponge with Vertically Aligned Channels for Highly Efficient and Salt-Resistant Solar Desalination.

Solar-assisted interfacial evaporation is a promising approach for purifying and desalinating water. As a sustainable biomass material, wood has attracted increasing interest as an innovative substrate for solar desalination, owing to its intrinsic porous structure, high hydrophilicity, and low thermal conductivity. However, developing wood-based solar evaporators with high evaporation rates and excellent salt resistance still remains a significant challenge, owing to the absence of large pores with high interconnectivity in natural wood. Herein, by converting the honeycombed structure of natural wood into a lamellar architecture via structural engineering, we develop a flexible wood sponge with vertically aligned channels for efficient and salt-resistant solar desalination after surface coating with carbon nanotubes (CNTs). The special lamellar structure with an interlayer distance of 50-300 μm provides the wood sponge with faster water transport, lower thermal conductivity, and water evaporation enthalpy, thus achieving higher evaporation performances in comparison with the cellular structure of natural wood. Noteworthy, the vertically aligned channels of the wood sponge facilitate sufficient fluid convection and diffusion and enable efficient salt exchanges between the heating interface and the underlying bulk water, thus preventing salt accumulation on the surface. Benefiting from the distinctive lamellar structure, the developed wood-sponge evaporator exhibits exceptional salt resistance even in a hypersaline brine (20 wt %) during continuous 7-day desalination under 1 sun irradiation, with a high evaporation rate (1.38-1.43 kg m-2 h-1), outperforming most previously reported wood-based evaporators. The lamellar wood sponge may provide a promising strategy for desalinating high-salinity brines in an efficient manner.

Evidence for developmental vascular-associated necroptosis and its contribution to venous-lymphatic endothelial differentiation.

During development, apoptosis removes redundant cells and ensures proper organ morphogenesis. Necrosis is long known as an adult-bound inflammatory and pathologic cell death. Whether there exists physiological necrosis during early development has been speculated but yet clearly demonstrated. Here, we report evidence of necroptosis, a type of programmed necrosis, specifically in perivascular cells of cerebral cortex and skin at the early stage of development. Phosphorylated Mixed Lineage Kinase Domain-Like protein (MLKL), a key molecule in executing necroptosis, co-expressed with blood endothelial marker CD31 and venous-lymphatic progenitor marker Sox18. Depletion of Mlkl did not affect the formation of blood vessel network but increased the differentiation of venous-lymphatic lineage cells in postnatal cerebral cortex and skin. Consistently, significant enhancement of cerebrospinal fluid diffusion and lymphatic drainage was found in brain and skin of Mlkl-deficient mice. Under hypobaric hypoxia induced cerebral edema and inflammation induced skin edema, Mlkl mutation significantly attenuated brain-blood-barrier damage and edema formation. Our data, for the first time, demonstrated the presence of physiological vascular-associated necroptosis and its potential involvement in the development of venous-lymphatic vessels.

A top-down control on upper crustal inheritance on the south-eastern Tibetan Plateau

Mantle tectonics, such as asthenospheric upwelling and lithospheric decoupling, usually controls subsequent fluid formation and migration from deep to shallow levels in the lower lithosphere and promotes rock failure and deformation. Based on the concept whereby the fluid migration location defines the structural inheritance, we aim to relate crustal processes to mantle tectonics using fluids revealed by a new magnetotelluric (MT) array across the Ailao Shan-Red River belt. As imaged via a 3D resistivity model, two lower-lithospheric conductive anomalies are determined as consistent with the Dian-Qiong (DQ) suture and Song Da (SD) belt and interpreted to contain interconnected melt. Because potassic magmatism was enabled by partial melting in the lower lithosphere, we could infer that the DQ and SD have reworked as the major fluid migration channels. Fluid migration is considered to drive lithospheric decoupling at a low-viscosity conductive layer, which is inferred feeding by aqueous and melt fluids originating from the two channels and diffusing at depths from 15 to 20 km. Constrained by the geochronology results, this weak layer could have provided convenience to induce the entirely upper crustal translation-rotation within the time interval between potassic magmatism and strike-slip of the Red River fault. This translation-rotation process is inherited from the underlying mantle processes and may further be remotely affected by the upper crustal movement of the Tibetan Plateau, conforming with the crustal rotation observed to the north of our study region. This work provides a compelling example of the tectonic control of the mantle on inherited responses in the crust.Plain Language Summary Crustal deformation is usually controlled by mantle tectonic processes, especially the southeastern Tibetan Plateau. Some models have proposed that lithospheric shearing and lower-crustal flow have controlled the crustal deformation in the Cenozoic. However, crustal rotation models show less possibility of a channel flow and relate the crustal deformation to the remote effect of India-Asia collision. Our study investigates above hypotheses by imaging the electrical resistivity of rocks beneath the major Red River Fault area in southeastern Tibet, using magnetotelluric data with high quality in a dense array. The lithosphere of the study area is interpreted to have been divided into two horizontal systems by a fluid diffusion layer at the bottom of upper crust. Resistivity low in the lower lithosphere is inferred due to partial melting of deep lithosphere and reworking of the paleo sutures in the Late Cenozoic, which have spread at the bottom of upper crust. Rather than the channel flow, this fluid migration process sensitively reflected in our model relates the mantle tectonics to crustal rotation by providing rheological conditions. We, hence, propose an inherited structure model featured by lithospheric decoupling and upper-crustal translation-rotation that may occur before the major strike-slip event.

Surface and subsurface structural mapping for delineating the active emergency spillway fault, Aswan, Egypt, using integrated geophysical data

The High Dam is one of the world’s biggest embankments dams. Moreover, the new city of Aswan, which locates on the western side of the Nile River, is one of the cities that was established to overcome the growing population problem. Therefore, the detailed geophysical studies for the active faults are of more importance for assessing the seismic stability for both of them. Indeed, the emergency spillway fault was documented as a normal and inactive fault. While, a moderate earthquake (ML = 4.6) was recorded along this fault in 2010, about 4.5 km away from the Dam. Hence, its activity must be re-evaluated. The seismic activity along the fault and its extension has been studied. The seismicity distributions and the fault plane solution indicate normal faulting with a strike-slip component and shallow focal depth. Moreover, pore pressure and fluid diffusion play an essential role in fault activation process. On the other hand, the magnetic data for the research area was subjected to a detailed analysis. 2D spectrum analysis and 3D Euler deconvolution methods, were used to analyze and interpret the aeromagnetic anomaly data so as to better understand the tectonic framework of the study region. Finally, the integrated geophysical data delineate the trend of the emergency spillway fault which extends NW–SE. This fault could assist in updating the current seismic source model around the High Dam and new Aswan city for evaluating the seismic hazard for both of them.

Effects of water injection on the stress field in the changning shale gas field, Sichuan Province, southwest China

It is generally considered that injection-induced seismicity is related to injection duration, injection volume, geological settings, and spatial relationships between the wells and preexisting faults. The seismicity in the Changning shale gas field, which is the largest shale gas field in China, has increased significantly since 2012. A 3D finite element model based on this area is established in our study for calculating the effect of injection on the regional stress field. The modelling results show that the permeability of sedimentary rock is a key factor for determining the fluid diffusion range and affects the stress field in deeper strata by controlling the gravity load. This effect is sufficient to induce earthquakes under critical conditions. Under a reasonable permeability (1.45 × 10−15 m2), injection may induce shallow-focus earthquakes (<3 km) by pore pressure increase and deep-focus earthquakes by increasing the gravity load. In addition, the low-permeability detachment surface below the injection well may buffer the perturbation of the stress field beneath it during injection.

Schmidt-number effects on the flow past a sphere moving vertically in a stratified diffusive fluid: Revisited

The effects of the Schmidt number (Sc) on the flow past a sphere descending in a stratified fluid are investigated using high-resolution numerical simulations over a wide range of Sc(0.7≤Sc≤2000). The results indicate that the buoyant jet appearing above the sphere is strongly influenced by density diffusion as well as buoyancy, and it becomes stronger and thinner with increasing Schmidt number. Scaling laws are derived and validated for the radius of the buoyant jet and thickness of the density boundary layer on the sphere. The former, characterized by significant density diffusion, is proportional to Fr/(ReSc), where Re[=W*(2a*)/ν*] is the Reynolds number and Fr[=W*/(N*a*)] is the Froude number (a* is the radius of the sphere, W* is the descending velocity of the sphere, ν* is the kinematic viscosity of the fluid, and N* is the Brunt–Väisälä frequency). The latter is similar to that of the passive scalar with a high Schmidt number (∝Re−1/2Sc−1/3), but a better estimate Re−1/2Fr1/4Sc−3/8 can be obtained by assuming a balance between buoyancy and viscous forces in the velocity boundary layer.

InSAR Observations Reveal Variations in Shallow Creep on the Kangding Segment of the Xianshuihe Fault

AbstractInvestigating the spatiotemporal characteristics of aseismic shallow creep provides insights into interseismic steady-state and/or postseismic transient behavior of faults. In this study, we focus on the Kangding segment of the Xianshuihe fault in eastern Tibet, where the 2014 Mw 5.9 Kangding earthquake occurred. Previous geodetic observations in 1999–2021 identified apparent shallow creep along this segment; however, whether the aseismic slip is secular creep, afterslip of the 2014 Kangding earthquake, or the combined effect remains unresolved. We process descending and ascending Interferometric Synthetic Aperture Radar data in the 2014–2021 period and investigate the creep rate variations on the fault plane. Our results reveal an ∼55-km-long aseismic slip section between Huiyuan Temple and Kangding Airport, of which the ∼15-km-long section between Huiyuan Temple and Jinlong Temple is in steady creep at a rate of 13 ± 2.0 mm/yr. Along the remaining ∼40-km-long section that overlaps the rupture of the Kangding earthquake, the creep rate decays from ∼40 to 0 mm/yr between 2014 and 2019, implying that the aseismic slip here is most likely the postseismic afterslip. We also identify a northwestward migration of aseismic creep from Huiyuan Temple to Longdengba during 2017–2021, which might be related to fluid diffusion. On the basis of the aseismic slip distribution, we quantitatively calculate the moment budget on the Kangding segment. The results show that the Huiyuan Temple-Longdengba section can produce an Mw 6.9 earthquake. Despite the 2014 Kangding earthquake, which ruptured the ∼40-km-long Jinlong Temple-Kangding Airport section, the accumulated seismic moment since the last major earthquake in 1748 is still sufficient for an Mw 7.0 earthquake.

Hydraulic fracturing process in rocks – small-scale simulations with a novel fully coupled DEM/CFD-based thermo-hydro-mechanical approach

In the paper, a two-dimensional (2D) numerical simulation of a small-scale hydraulic fracturing process in rock specimens possessing a single injection slot was conducted. A unique DEM/CFD-based pore-scale thermal-hydro-mechanical (THM) model was used to simulate two-phase laminar fluid flow (water and gas) with heat transfer in non-saturated porous materials with low porosity. Using a DEM fully coupled with CFD (based on a fluid flow network composed of channels in a continuous domain between discrete elements) and heat transfer at the mesoscale, a series of numerical calculations for small cohesive granular specimens of simplified spherical mesostructure with one injection slot were carried out. Plane strain compression conditions were assumed. Both the fluid (diffusion and advection) and bonded particles (conduction) were involved in heat transfer. The impacts of the fluid's dynamic viscosity, gas phase content, and temperature difference between the rock matrix and the fluid injection on the process of hydraulic fracture initiation and propagation were all examined in-depth. It was discovered that those effects were all of great significance to the behaviour of a single hydraulic fracture.

Hilbert expansion based fluid models for kinetic equations describing neutral particles in the plasma edge of a fusion device

Neutral particles in the plasma edge of fusion devices based on magnetic confinement are described by a transient kinetic equation incorporating ionization, recombination, and charge-exchange collisions. In charge-exchange dominated regimes, the neutral particle velocity distribution approaches the drifting Maxwellian defined by the mean velocity and temperature of the plasma. This enables model order reduction from the kinetic equation to approximate fluid models. We derive transient fluid models consistent with the kinetic equation by exploring a splitting based approach. We split the kinetic equation in sources and sinks on the one hand, and transport combined with charge-exchange on the other hand. Combining transport with charge-exchange collisions allows for deriving Hilbert expansion based fluid models. The retrieved fluid models depend on the assumed importance (scaling) of the different terms in the split equation describing transport and charge-exchange. We explore two scalings: the hydrodynamic scaling and the diffusive scaling. The diffusive scaling fluid model closely resembles phenomenological fluid models for describing neutral particles in the plasma edge that have been derived in the past. Therefore, the Hilbert expansion based fluid models can serve as a theoretical basis for such phenomenological fluid models and elucidate some of their properties. The performance of the fluid models with respect to a discrete velocity model and a Monte Carlo reference solver is assessed in numerical experiments. The code used to perform the numerical experiments is openly available.

Gravity field changes reveal deep mass transfer before and after the 2013 Lushan earthquake

The 2013 MS7.0 Lushan earthquake, Sichuan, China, occurred on a blind thrust fault in the southern Longmenshan fault belt. The terrestrial hybrid repeated gravity observation enables us to investigate the redistribution of both surface and deep mass. Here, we find a transient increase in the gravity field about 2 years before the earthquake and a drop after the mainshock. A Bayesian inversion method with spatiotemporal smoothness is employed to extract the apparent density changes. The increase of apparent density on the south of the focal zone is assumed to be related to crustal mass transfer. We introduce a disc-shaped equivalent source model with a homogeneous density to address this hypothesis, and estimate the model parameters by Markov Chain Monte Carlo simulations. As a fluid diffusion footprint is indicated by the seismicity migration in this region, with a fitted diffusion rate of 10 m2 s−1, we conclude that such deep crustal mass transfer may be caused by fluid diffusion.

Impact of tiny nanoparticles on generalized Eyring–Powell liquid subject to activation energy

Due to innumerable applications of nanofluid in heat transfer phenomena as well as engineering processes, the research on this innovative fluid over conventional fluid got popularity among researchers. Here, we have considered a non-Darcy porous surface medium for generalized Eyring–Powell fluid model under thermophoretic as well as Brownian movements. No mass flux phenomena along with heat sink-source and activation energy aspects are scrutinized; characteristics of random motion of fluid and thermophoresis diffusion characteristics for generalized Eyring–Powell fluid are examined briefly. The system of nonlinear PDEs is reduced to nonlinear ODEs by using the similarity variable technique; the numerical scheme bvp4c is used along with shooting technique. The physical aspects like flow of fluid, temperature profile, concentration for variation of concerned parameters have been computed and demonstrated pictorially with the help of graphs. It is observed that the velocity of nanofluid declines by increasing values of the power law index ([Formula: see text] and Eyring–Powell liquid parameters. Augmented values of Brownian moment, thermophoresis parameter as well as heat source rise with increase in temperature of nanofluid. The concentration profile of generalized Eyring–Powell nanofluid deteriorates for higher values of Schmidt number. Moreover, the transportation rate of heat declines against Pr, while it rises by increasing values of [Formula: see text].

Deformation of corrugated hydrogel panel subject to chemo-mechanical coupled loading

In this paper, a novel plate theory is proposed for corrugated soft panels with a chemically coupled constitutive model of hydrogel, which is formulated via perturbation analysis on the physically based constitutive theory. Here, the elastic moduli naturally incorporate the chemical effects that could reduce to the classical linear Hookean law or second-order Murnaghan model. As a result, the resultant constitutive model is concise in form and comprehensive in physical integrity, where no further coupling is required between the deformation of solid and diffusion of fluid. Applying the symplectic elasticity method, the exact bending solution is then derived for corrugated hydrogel panels with two opposite sided clamped. The main effects of chemical potential, Flory parameter, and geometric factors on the equivalent stiffnesses and transverse deflections are investigated in detail. Some new results could be used as a reference for the designing of flexible and wearable devices.

Shear-wave splitting patterns in Perachora (Eastern Gulf of Corinth, Greece)

The Eastern Gulf of Corinth (EGoC) is one of the most seismically active areas in Greece. It is monitored by local and regional seismic stations of the Hellenic Unified Seismic Network (HUSN). In 2020, a high-yield seismic sequence, lasting over five months, occurred at the Perachora peninsula. This provided a unique opportunity to investigate the anisotropic properties of the upper crust in the area, which lacks relevant studies. The sequence exhibited characteristics of a seismic swarm, with the strongest event having a magnitude of 3.7. In the herein analysis, we use recordings from suitable HUSN stations for two periods: (a) 2008 to 2019, a period of scarce seismicity, to identify background anisotropy and (b) the 2020 seismic swarm period. We used a fully automated method to measure shear-wave splitting properties. After considering a shear-wave window of 45° and several quality criteria, we determined a complex state of anisotropy, with NE-SW directions of polarization (𝜑) prevailing pre-2020, while a dominant WNW-ESE orientation was observed during the swarm (with secondary NE-SW and N-S trends). The spatial distribution of 𝜑 did not offer any strong correlation with local faults. Additionally, 𝜑 seemed to rotate in 2015 and 2020, with variations of normalized time-delays being present during the crisis. These observations, along with indications regarding fluid diffusion during the swarm, led us to hypothesize that shear-wave splitting in the EGoC is mainly driven by high pressure gradients. A better understanding of pre‑2020 seismicity and more local stations to record future seismicity would be required to further specify the connection between fluid processes and seismic anisotropy in the area.

Magnetic diffusion of time distributed-order Maxwell fluid in boundary layer under the action of induced magnetic field

Hydrogel has been widely used in energy storage devices and flexible electronic equipment. To promote its applications, a laminar boundary layer model is proposed to analyze the velocity and temperature distributions in the mold. Based on the time distributed-order Maxwell and Cattaneo constitutive relations, the research establishes governing equations of unsteady two-dimensional incompressible viscoelastic electrically conducting hydrogel taking into account the induced magnetic field. When the magnetic Reynolds number is large enough, it is necessary to consider the magnetic diffusion in the boundary layer. The effects of thermal radiation and velocity slip are also considered at the same time. The Gauss quadrature rule is used to approximate the distributed-order integral, and then the numerical solution of the model is obtained by using the finite difference method and the L1-algorithm. The analytical solution is constructed to verify the effectiveness of the numerical solution. The results show that the fluid velocity decreases with the increment of magnetic parameter, while the induced magnetic field increases. The boundary layer thickness of velocity, induced magnetic field, and thermal becomes thinner with the enlargement of velocity and temperature relaxation time parameters. Moreover, the distributed-order and the fractional constitutive models are compared through different weight coefficients, and it is found that the fractional constitutive model obtains larger velocity and temperature distributions.

Fin systems comparative anatomy in model Batoidea Raja asterias and Torpedo marmorata: Insights and relatioships between musculo-skeletal layout, locomotion and morphology.

The macroscopic and microscopic morphology of the appendicular skeleton was studied in the two species Raja asterias (order Rajiformes) and Torpedo marmorata (Order Torpediniformes), comparing the organization and structural layout of pectoral, pelvic, and tail fin systems. The shape, surface area and portance of the T. marmorata pectoral fin system (hydrodynamic lift) were conditioned by the presence of the two electric organs in the disk central part, which reduced the pectoral fin surface area, suggesting a lower efficiency of the "flapping effectors" than those of R. asterias. Otherwise, radials' rays alignment, morphology and calcification pattern showed in both species the same structural layout characterized in the fin medial zone by stiffly paired columns of calcified tiles in the perpendicular plane to the flat batoid body, then revolving and in the horizontal plane to continue as separate mono-columnar rays in the fin lateral zone with a morphology suggesting fin stiffness variance between medial/lateral zone. Pelvic fins morphology was alike in the two species, however with different calcified tiles patterns of the 1st compound radial and pterygia in respect to the fin-rays articulating perpendicularly to the latter, whose tile rows lay-out was also different from that of the pectoral fins radials. The T. marmorata tail-caudal fin showed a muscular and connective scaffold capable of a significant oscillatory forward thrust. On the contrary, the R. asterias dorsal tail fins were stiffened by a scaffold of radials-like calcified segments. Histomorphology, heat-deproteination technique and morphometry provided new data on the wing-fins structural layout which can be correlated to the mechanics of the Batoid swimming behavior and suggested a cartilage-calcification process combining interstitial cartilage growth (as that of all vertebrates anlagen) and a mineral deposition with accretion of individual centers (the tiles). The resulting layout showed scattered zones of un-mineralized matrix within the calcified mass and a less compact texture of the matrix calcified fibers suggesting a possible way of fluid diffusion throughout the mineralized tissue. These observations could explain the survival of the embedded chondrocytes in absence of a canalicular system as that of the cortical bone.

Complexity of initiation and evolution of the 2013 Yunlong earthquake swarm

3D fault geometry has recently been shown to play a key role in controlling the kinematics of earthquake swarms. With the aid of a temporary dense seismic array, machine-learning-based detection, and accurate relocation, we outline a complex 3D fault zone accommodating a small earthquake swarm near Yunlong city, western Yunnan, China from February to May 2013. Our results show that the swarm initiated from a compressive stepover zone and subsequently activated a complex fault zone including six planar fault segments. The migration front of the swarm can be well-modeled by fluid diffusion, indicating the swarm was primarily driven by pressurized fluid. A nearby GPS site exhibits a slight displacement that started immediately before the swarm, then gradually decayed in the following months, implying the stress fluctuations caused by a possible aseismic slip likely initiated the swarm and, along with fluid diffusion, drove the migration of the swarm. Within the stepover zone, complex and dense fractures act as conduits connecting the reservoir and fault zone, facilitating fluid flow. Meanwhile, the stress in the stepover zone tends to increase in response to the compression of the two boundary faults, which not only makes the stepover zone more susceptible to be triggered by those transient stresses but also forms a fluid pumping mechanism that drives fluids from the stepover zone into the complex fault zone. We suggest the complexity of the initiation and evolution of the 2013 Yunlong swarm is strongly controlled by 3D fault geometry.

Temperature Dependent Viscosity Effect on Oscillatory Mode of Darcy-Rayleigh Convection in a Double Diffusive Binary Viscoelastic Fluid Saturated Anisotropic Porous Layer

An anisotropic porous layer saturated with a viscoelastic double diffusive binary fluid is examined numerically for the onset of Darcy-Rayleigh convection. From below, the system is heated, while from above, it is cooled. The temperature-dependent viscosity was added to the double diffusive binary fluid, and the Galerkin expansion method was used to determine the critical Darcy-Rayleigh number. When their values are raised, the impacts of strain retardation, thermal anisotropy parameter and Dufour number slow the production of heat transfer and stabilise the system. When the values are increased, the stress relaxation, Darcy-Prandtl, mechanical anisotropy parameters, temperature dependent viscosity and Soret number accelerate the heat transfer process in convection, which destabilises the system

Galerkin scheme on entropy generation in complex fluid involving gyrotactic microorganisms on cylinder/surface via solar thermal radiations

In the current analysis, numerical investigation for double diffusion and gyrotactic microorganisms in complex fluid involving Dufour and Soret influences over stretching cylinder, and stretching surface is investigated new research in recent developments and analysis of such problems are not observed yet in the open literature. Mechanisms of thermal radiation, heat sink, viscous dissipation, chemical reaction and Joule heating are incorporated. Solar water heating, solar cooking, solar power generation and solar desalination are a few examples of practical uses for solar thermal processes. Applications of the current analysis include thermal insulation, biomedical engineering, chemical processing, food preservation, cooling systems and power generation. Moreover, the utilization of a uniform magnetic field is incorporated along the z-direction under consideration of magnetic Reynolds number (low). Such development has been utilized in several industrial and technological applications. This modern physical development is transformed in mathematical modeling regarding highly coupled non-linear PDEs. A set of PDEs (non-linear) is transformed into dimensionless form regarding non-linear ODEs utilizing relevant variables and a numerical solution is achieved using finite element methodology. In this development, essential simulations have been obtained, for example, surface drag force, Nusselt number, mass diffusion rate and microorganism concentration.

Stress‐Based and Convolutional Forecasting of Injection‐Induced Seismicity: Application to the Otaniemi Geothermal Reservoir Stimulation

AbstractInduced seismicity observed during Enhanced Geothermal Stimulation at Otaniemi, Finland is modeled using both statistical and physical approaches. The physical model produces simulations closest to the observations when assuming rate‐and‐state friction for shear failure with diffusivity matching the pressure build‐up at the well‐head at onset of injections. Rate‐and‐state friction implies a time‐dependent earthquake nucleation process which is found to be essential in reproducing the spatial pattern of seismicity. This implies that permeability inferred from the expansion of the seismicity triggering front (Shapiro et al., 1997, https://doi.org/10.1111/j.1365-246x.1997.tb01215.x) can be biased. We suggest a heuristic method to account for this bias that is independent of the earthquake magnitude detection threshold. Our modeling suggests that the Omori law decay during injection shut‐ins results mainly from stress relaxation by pore pressure diffusion. During successive stimulations, seismicity should only be induced where the previous maximum of Coulomb stress changes is exceeded. This effect, commonly referred to as the Kaiser effect, is not clearly visible in the data from Otaniemi. The different injection locations at the various stimulation stages may have resulted in sufficiently different effective stress distributions that the effect was muted. We describe a statistical model whereby seismicity rate is estimated from convolution of the injection history with a kernel which approximates earthquake triggering by fluid diffusion. The statistical method has superior computational efficiency to the physical model and fits the observations as well as the physical model. This approach is applicable provided the Kaiser effect is not strong, as was the case in Otaniemi.