Wave Processes Research Articles

Lower Band Chorus Wave Scattering Causing the Extensive Morningside Diffuse Auroral Precipitation During Active Geomagnetic Conditions: A Detailed Case Study

AbstractThe diffuse aurora is a natural phenomenon observed over the Earth's polar region. Compared with the nightside diffuse aurora, the brightness of the dayside diffuse aurora (0600–1800 magnetic local time (MLT)) is relatively weak, thus requiring more stringent observation conditions. Therefore, the current understanding of what causes the dayside diffuse aurora is still quite limited. Here, we present an intense morningside diffuse aurora (0600–1000 MLT) event observed on 1 January 2016 during the recovery phase of the substorm, using conjugate observations of wave and particle spectrum from the Radiation Belt Storm Probes and auroral emission from the Special Sensor Ultraviolet Spectrographic Imagers on the Air Force Defense Meteorological Satellite Program (DMSP/SSUSI). We perform calculations of diffusion coefficients and simulations of the electron fluxes for this event. Our results show that the chorus waves are the primary contributors to the formation of the morningside diffuse aurora, with precipitated electron energies ranging from a few keV to tens of keV. The lower band chorus shows significant pitch angle scattering efficiency for electrons with energies from 5 to 20 keV. The upper band chorus waves induce acceleration effects on 1–20 keV electrons. We suggest that the upper band chorus waves accelerate low‐energy electrons to higher energies, enabling them to engage in the scattering process of the lower band chorus waves. Our study makes a contribution to recent research on the formation mechanisms of diffuse aurora and deepens our understanding of wave‐particle interactions leading to dayside electron precipitation.

Non-contacting laser-based acousto-seismics at the laboratory scale: towards near-real-time monitoring of granular analogue models

SUMMARY In this work we present a novel, experimentally efficient set-up for performing non-contacting laser vibrometry on geologic materials and their analogues. We show it is possible to acoustically monitor a granular material experiment in real time compared to the typical timescale of analogue modelling experiments. We acquire non-contacting waveform data with consistently high signal-to-noise ratio. Compared to previously used standard contacting transducers, the novel joint use of sources and receivers that are both laser-based resulted in measured signals with improved waveforms and temporal bandwidths. These data acquisition improvements, in our case where surface waves are prominent in the data, enable enhanced multichannel surface wave processing, for example, in terms of reliable dispersion curve estimates. We find, given the high waveform fidelity of our acquisition system, that the observed surface waves are highly sensitive to relatively small changes in the medium’s elastic properties, making them a demonstrably reliable to monitor any processes that affect elasticity in these models in near real time. As a demonstration, we continuously monitor a scaled analogue model containing granular glass beads. By continuously monitoring—that is, performing repeatable active-source acousto-seismic surveys at short time-lapse intervals—over a period of 10 hr, we find that an increase of relative humidity of 10 per cent can lead to as much as a factor of two increase in surface wave group velocities. Finally, we discuss future applications of the developed method by considering surface wave inversion for fault and stress monitoring during the deformation of a model.

Effects of Floating States on Collision Forces of Drifting Containers Caused by Solitary Wave Inundation

The overtopping-inundation process of a tsunami results in the collisions of drifting objects on the coast, which damage structures, thereby increasing the risk of collapse. This study conducted laboratory experiments on the collision between a drifting container caused by the overtopping-inundation process of a solitary wave and a fixed port crane’s leg. The movement trajectory and velocity of the container as well as the collision velocity by solitary wave inundation, were analyzed using motion analysis software. Overall, increasing solitary wave scale, collision velocity, and drifting object weight and decreased distance between the two objects tended to increase the collision force. However, different experiment results were also obtained due to pitching in objects that fully floated without bottom friction owing to the solitary wave bore. This resulted in line-to-surface collisions. Thus, surface-to-surface contact occurred under the incomplete floating condition owing to the difficulty because of interference with the bottom; however, the collision force decreased under complete floating conditions owing to line-to-surface contact. Therefore, the contact condition according to the floating behavior must be considered a parameter while predicting the collision forces of drifting objects. Thus, surface-to-surface contact occurred under the incomplete floating condition owing to the difficulty because of interference with the bottom; however, the collision force decreased under complete floating conditions owing to line-to-surface contact. Therefore, the contact condition according to the floating behavior must be considered a parameter while predicting the collision forces of drifting objects.

Hard- and Software Controlled Complex for Gas-Strain Monitoring of Transition Zones.

The article describes a hard- and software controlled complex for gas-strain monitoring, consisting of stationary laser strainmeters and a laser nanobarograph, a stationary gas analyzer, and a weather station installed at Shultz Cape in the Sea of Japan; and a mobile shipboard complex, consisting of a gas analyzer and a weather station installed in a scientific research vessel. In the course of trial methodological measurements on these systems, general patterns were identified in the dynamics of greenhouse gases and deformation of the Earth's crust in the range of diurnal and semi-diurnal tides, and also in the range of ultra-low frequencies, caused by atmospheric wave processes and, possibly, individual tones of the Earth's eigen oscillations.

Effect of Combined Laser Thermal and Shock Wave Effects on the Mechanical and Tribological Properties of Steels.

Herein, we present the results of an experimental study on the mechanical properties of Fe-C alloys with different carbon contents (0.2, 0.45, and 0.8%) in a wide range of deformation rates (10-3-103 s-1) and abrasive wear resistance, which underwent combined laser thermal (laser surface hardening-LSH) and laser shock wave (Laser Shock Peening-LSP) processing. The combined treatment modes included a different sequence of exposure to laser thermal and laser-induced shock pulses on the material. The amplitude and duration of laser-induced shock waves were measured using a laser Michelson interferometer. The mechanical properties of steel samples were studied under conditions of uniaxial tension under static loads on a standard universal testing machine, the LR5KPlus, and under dynamic loading, tests were carried out on a specialized experimental complex according to the H. Kolsky method using a split Hopkinson rod. The abrasive wear resistance of hardened surfaces was studied using the Brinell-Haworth method. Studies have shown that the use of a combination of LSH and LSP treatments leads to an increase in both the mechanical properties of steels and abrasive wear resistance compared to traditional laser hardening. It has been established that in the combinations considered, the most effective is laser treatment, in which LSP treatment is applied twice: before and after LSH. Thus, after processing steels using this mode, an increase in the depth of the hardened layer was recorded-by 1.53 times for steel 20, by 1.41 times for steel 45, and by 1.29 times for steel U8-as well as a maximum increase in microhardness values by 22% for steel 20, by 27% for steel 45, and by 13% for U8 steel. The use of this mode made it possible to obtain the maximum strength properties of the studied materials under static and dynamic loading, which is associated with an increase in the volume fraction of the strengthened metal and high microhardness values of the strengthened layer of traditional LSH. The dependences of abrasive wear of the studied steels after various combinations of LSP and LSH impacts were established. It is shown that the greatest wear resistance of the studied steels is observed in the case when the LSH pulse is located between two LSP pulses. In this case, abrasive wear resistance increases by 1.5-2 times compared to traditional LSH.

A Synchrosqueezed Transform Method Based on Fast Kurtogram and Demodulation and Piecewise Aggregate Approximation for Bearing Fault Diagnosis.

Synchrosqueezed transform (SST) is a time-frequency analysis method that can improve energy aggregation and reconstruct signals, which has been applied in the fields of medical treatment, fault diagnosis, and seismic wave processing. However, when dealing with time-varying signals, SST suffers from poor time-frequency resolution and is unable to deal with long signals. In order to accurately extract the characteristic frequency of variable speed rolling bearing faults, this paper proposes a synchrosqueezed transform method based on fast kurtogram and demodulation and piecewise aggregate approximation (PAA). The method firstly filters and demodulates the original signal using fast kurtogram and Hilbert transform to reduce the influence of background noise and improve the time-frequency resolution. Then, it compresses the signal by using piecewise aggregate approximation, so that the SST can deal with long signals and, thus, extract the fault characteristic frequency. The experimental data verification results indicate that the method can effectively identify the fault characteristic frequency of variable-speed rolling bearings.

Modelling Turbulent Flows near Coastal Structures Using Various Turbulence Models

Introduction. The reduction in beach width due to erosion is a significant issue that can either be mitigated or exacerbated by coastal protection structures. Modelling breaking waves near the coast and around coastal structures can be used to determine their impact on the dynamics of the coastal zone. The objective of this study is to model and analyze the dynamics of turbulent structures around a single breakwater, obtained using two turbulence modelling schemes: RANS and LES.Materials and Methods. Turbulence induced by breaking waves was investigated. The modelling was based on bathymetric measurements conducted along the Azov Sea coast and a three-dimensional wave hydrodynamics model supplemented with various turbulence calculation configurations.Results. Modelling results of wave processes generating turbulent flows in the presence of coastal protection structures using different turbulence models were obtained. Results obtained based on Reynolds-averaged Navier-Stokes (RANS) equations are compared with the results of Large Eddy Simulation (LES) approach with Smagorinsky dynamic subgrid-scale model (DSM).Discussion and Conclusions. The results showed that wave heights simulated by LES were higher than those simulated by RANS in the front and leeward regions of the coastal protection structure and were lower in its upper part. Thus, according to LES, a greater amount of wave energy was preserved after passing over the breakwater. Velocity vectors of the water medium showed the formation of a vortex when LES was used, whereas no evidence of such turbulent vortices was detected in the case of RANS, confirming the better performance of LES for turbulence modelling in the coastal zone. According to the presented results, LES is the preferred tool for generating turbulence under incoming wave conditions in engineering practices.

Radiation Process in Relativistic MHD Waves: The Case of Circularly Polarized Alfvén Waves

Turbulence in highly magnetized plasma can be relativistic and induce an electric field comparable to the background magnetic field. Such a strong electric field can affect the emission process of nonthermal electrons. As the first step toward elucidating the emission process in relativistic turbulence, we study the radiation process of electrons in relativistic circularly polarized Alfvén waves. While the induced electric field boosts the average energy of low-energy electrons with a Larmor radius smaller than the wavelength, the emissivity for such electrons is suppressed because of the elongated gyromotion trajectory. The trajectory of high-energy electrons is shaken by the small-scale electric field, which enhances the emissivity. Since the effective Lorentz factor of E × B drift is ≃2 in the circularly polarized Alfvén waves, the deviation from the standard synchrotron emission is not so prominent. However, a power-law energy injection in the waves can produce a concave photon spectrum, which is similar to the GeV extra component seen in GRB spectra. If the turbulence electric field is responsible for the GeV extra component in GRBs, the estimates of the typical electron energy and magnetic field should be largely altered.

A modified weakly compressible smoothed particle hydrodynamics mixture model for accurate simulation of wave and porous structure interaction

In this study, a modified weakly compressible smoothed particle hydrodynamics (WCSPH) mixture model was developed to more accurately simulate the interaction between waves and porous structures. In this model, we enhanced the governing equations of the traditional WCSPH mixture model by introducing Darcy velocity, apparent density, and an adjustable smoothing length. This refinement ensures that the modified model effectively maintains the conservation of fluid volume in seepage simulations. Additionally, this paper proposes a permeable interface treatment technique that replaces traditional smoothed particle hydrodynamics interpolation with finite element shape function interpolation, significantly enhancing computational efficiency. At the same time, we also introduced and revised a particle shifting technique, which further increases the computational precision of the model. The modified WCSPH mixture model was then applied to simulate several physical experiments, including the dam-break wave propagation in a permeable dam, the attenuation of solitary waves on a permeable riverbed, the propagation of the solitary wave on a submerged porous structure, and the breaking process of waves passing through permeable breakwaters. Through comparison with the experimental data and other numerical results, the current model was comprehensively verified from various aspects, such as fluid volume conservation, wave evolution in and around the porous structure, and pressure distribution characteristics. The results confirm the excellent performance of the current model in simulating the interaction between waves and porous structures.

Unsteady Wave Processes in a Cylinder Made of Viscoelastic Functionally Graded Material

Unsteady Wave Processes in a Cylinder Made of Viscoelastic Functionally Graded Material

Computing Speed-of-Sound From Ultrasound: User-Agnostic Recovery and a New Benchmark.

Medical ultrasound is one of the most accessible imaging modalities, but is a challenging modality for quantitative parameters comparison across vendors and sonographers. B-Mode imaging, with limited exceptions, provides a map of tissue boundaries; crucially, it does not provide diagnostically relevant physical quantities of the interior of organ domains.This can be remedied: the raw ultrasound signal carries significantly more information than is present in the B-Mode image. Specifically, the ability to recover speed-of-sound and attenuation maps from the raw ultrasound signal transforms the modality into a tissue-property modality. Deep learning was shown to be a viable tool for recovering speed-of-sound maps. A major hold-back towards deployment is the domain transfer problem, i.e., generalizing from simulations to real data. This is due in part to dependence on the (hard-to-calibrate) system response. We explore a remedy to the problem of operator-dependent effects on the system response by introducing a novel approach utilizing the phase information of the IQ demodulated signal. We show that the IQ-phase information effectively decouples the operator-dependent system response from the data, significantly improving the stability of speed-of-sound recovery. We also introduce an improvement to the network topology providing faster and improved results to the state-of-the-art. We present the first publicly available benchmark for this problem: a simulated dataset for raw ultrasound plane wave processing. The consideration of the phase of the IQ-signals presents a promising appeal to traversing the transfer learning problem, advancing the goal of real-time speed-of-sound imaging.

Research on internal explosion loads in folded arch tunnels: A theoretical approach

To elucidate the loading characteristics in the folded arch tunnel subjected to internal explosion, a field blast test was conducted in a large-scale (1:5) model constructed according to the immersed tube tunnel of Hong Kong-Zhuhai-Macao Bridge. The spatial distribution and time histories of the overpressure around the detonation point were recorded in the folded arch tunnel. The test data indicate that the internal blast loads in the folded arch tunnel is mainly attributed to the shock overpressure and gas overpressure. A fine FE model was developed in the LSDYNA platform, which was validated by the loading test data. The propagation process of blast waves and detonation products along the folded arch tunnel were studied by the developed model, which also helped reveal the interaction mechanism with the tunnel structure. Three existing theoretical models in predicting the internal blast loads were compared and assessed. It is found that the existing theoretical models developed for the internal blast loads has limitations in predicting the blast load in the tunnel, which especially would introduce a large error in manifesting the gas overpressure. A new loading model that enables precisely predicting the internal blast loads in the folded arch tunnel was proposed, which offers valuable insights for the blast-resistant design and disaster mitigation measures for the tunnel structure.

Evolution of Coniacian facies and environments in the Iberian basin: a longshore current controlling siliciclastic sand distribution on a carbonate platform

The Coniacian carbonate sediments of the Iberian basin were deposited on a homoclinal ramp that grades upwards into a distally steepened ramp, with a major shoreline siliciclastic fringe. Twenty-three facies have been identified and grouped into three main depositional environments: outer, mid, and inner ramp. The last include barrier (shoal), lagoon, carbonate tidal-flat and shoreface sub-environments. The more prominent biogenic components show a mixture of sunlight-dependent phototrophic organisms (mainly large benthic foraminifera) and nutrient-dependent heterotrophic organisms (mainly rudists), with a remarkable rare occurrence of corals. Nutrients supplied from the emergent mainland probably promoted the development of heterozoan organisms. The vertical evolution of the ramp shows: a basal transgressive stage with facies retrogradation; a maximum flooding stage, and a regressive stage with aggradation and progradation of a distally steepened ramp. The presence and distribution of siliciclastics are problematic, since sands coming into the basin are likely to be rapidly and widely redistributed along the basin, taking into account the common storm, wave, and tidal processes preserved by the sedimentary facies. The presence of a clockwise NW-flowing longshore current is postulated to account for this distribution, which was likely induced by both dominant external currents around Iberia and wind-driven currents. These clockwise gyres facilitated the invertebrate dispersion into this enclosed basin and the local presence of upwelling. This could have been another source of episodic nutrient-rich waters from the deep ramp, which may have favored heterozoan development even in the more proximal and relatively shallower-water facies.

Статистические характеристики расчета приращений сейсмической интенсивности при сейсмическом микрорайонировании горных территорий

Introduction. During seismic micro-zoning of a territory, one of the main instrumental methods for calculating intensity increments is the registration of earthquakes in areas with different soil conditions. In this case, the calculation of increments is based on the amplitudes of oscillations simultaneously in the given and reference sections. The purpose of the work is to compare the increments in various expressions obtained for powerful vibration and pulse sources, as well as for an instrumental measure of seismic intensity. Materials and methods. Processing of instrumental data, their systematization and description using basic statistical indicators. The analysis was carried out using data from the Vladikavkaz network - records of earthquakes obtained simultaneously at four seismic stations located in areas with different ground conditions. Results. To check the formulas for calculating seismic intensity increments and comparing them with the obtained data, distribution histograms and the corresponding probability density functions were constructed, under the assumption that the distribution is normal. All methods for calculating vibration amplitudes gave identical results in ranking areas according to the degree of seismic hazard, however, taking into account rounding, an increase in intensity by 1 point is not always achieved in an area where, due to the worst soil conditions. The best results for calculating intensity increments were obtained for the area values of the velocity and acceleration spectra. At the same time, the areas of the acceleration spectra provide better differentiation of soil conditions according to the degree of danger (with the same coefficient in front of the logarithm). Discussion. The task of developing an instrumental method of seismic micro-zoning is to clarify the coefficients in front of the logarithmic scale of the quantities under consideration, the reduction of which, in turn, determines the clarification of the level of impacts for given intensities. On the other hand, smaller coefficients lead to worse differentiation of soil conditions of areas when calculating increments of seismic intensity. The solution to the problem may lie somewhere at the junction of both approaches. Conclusion. Analysis of the results shows a connection between the magnitude of the distribution dispersion and the complexity of the engineering-geological conditions of the site. The more factors influence the wave processes in the soils, the greater the scatter of values around the average. Main factor is a multi-layered environment, i.e. the presence of reflective boundaries, and the other one is the very properties of the medium, i.e. its dispersion. Resume. Results are useful in differentiating soil conditions by an additional parameter that affects the probability of failure to exceed the calculated values of seismic impacts - the same average values of seismic intensity can be characterized by different confidence intervals; from a practical point of view, one should set the same probability of not exceeding the design impact values. Suggestions for practical applications and directions for future research. For practical applications it is necessary to distinguish the influence of the layering of the medium and the direct dispersion of the soils composing the stratum, which represents the next research task.

Wave attenuation and transformation across a highly turbid muddy tidal flat-salt marsh system

Understanding wave processes within the coastal system is crucial for the appropriate design of coastal prevention engineering and offshore structures. To address the limitations of field observations and traditional methods, an array of pressure sensors and optical instruments were deployed across a shoreward intertidal flat consisting of the fluid muddy seabed, bare flat, and salt marsh in a highly turbid coastal area. We found that the Spartina alterniflora salt marsh has the strongest wave dissipation capacity. Although bare flats have the weakest wave dissipation capacity, they are the most extensive within the intertidal zone, resulting in substantial total wave energy dissipation. A noteworthy positive feedback between fluid mud and wave dissipation is observed. Additionally, the incident waves undergo complex transitions during propagation, which are strongly modulated by tidal influences. In particular, when the wave propagation direction is opposite to the tidal current, there is an amplification of wave energy within the tidal flat. This amplification is attributed to the "jacking effect" of the tidal current, hindering the transformation of the wind waves into the low-energy capillary waves. It is important to note that the high-energy infragravity waves are gradually released and steadily increase as the incident waves propagate shoreward. This implies their potentially significant role in nearshore processes, especially during extreme dynamic events or along extensive coastlines.

Electrostatic Wave Decay in the Randomly Inhomogeneous Solar Wind

Despite a few space observations where Langmuir and ion acoustic waves are expected to participate in the mechanism of electrostatic decay, this is to date believed to be the main and fastest nonlinear wave process in the solar wind. However, in such a plasma where random density fluctuations are ubiquitous, the question of whether nonlinear wave processes play a significant role in Langmuir wave turbulence generated by electron beams associated with type III solar radio bursts remains still open. This paper provides several answers by studying, owing to two-dimensional challenging particle-in-cell simulations, the dynamics and the properties of the ion acoustic waves excited by such Langmuir wave turbulence and the role they play in the electrostatic decay. The impact on this process of plasma background density fluctuations and electron-to-ion temperature ratio is studied. Moreover, it is shown that, for a typical solar wind plasma with an average level of density fluctuations of a few percent of the ambient density and a temperature ratio of the order of 1, nonlinear induced scattering off ions occurs, with small intensity low-frequency quasi-modes and only in localized plasma regions where density is depleted or weakly perturbed by low-frequency turbulence.

A study of the non-linear properties and wave generation of the multi-layer non-hydrostatic wave model SWASH

Despite the increasing use of non-hydrostatic models in the study of wave processes in coastal regions, there is still limited understanding of the non-linear properties of the governing equations and how they improve with increased vertical resolution. In this study, the governing equations of the non-hydrostatic wave model SWASH are analysed and the linear and non-linear solutions up to third-order of all dependent variables are derived, considering one to four vertical layers. The analysis concludes that the model can achieve excellent non-linear properties with respect to the Stokes theory over a large range of water depths using only a few vertical layers. Furthermore, deriving solutions for all variables enables the formulation of improved wave generation and absorption boundary conditions for non-hydrostatic models. A well-known issue of non-linear wave models is related to the generation and propagation of spurious free waves, resulting to non-homogeneous wave fields. In this study, it is proven that by imposing the derived exact mathematical solutions of the governing equations at the model’s boundaries, the target first- and second-order wave profiles can be generated with high accuracy, while the spurious waves can be entirely eliminated.

Dynamic shock wave processing on β-MnMoO4 ceramic micro-sized crystals and its structure-morphology-property relations

In the present work, we perform a few shock-wave-processing experiments on typical ceramic materials of β-MnMoO4 (P2/c) by the exposure of 0, 100 and 200 shocks, respectively, and investigated their structural, optical and morphological features to materialize the effect of shock waves. Under shocked conditions, the title sample does not undergo any crystallographic phase transitions of either to α or to ω phases. However, several modifications are noticed in the mother phase such that the diffraction intensity ratio of (1-11)/(111) is found to have increased with respect to the number of shock pulses and the observed values are 0.85, 1.07 and 1.36 for the exposure of 0, 100, 200 shocks, respectively. Under the 200-shocked condition, the sample's intensity ratio is found to be closely matched to the standard pattern of the test sample with the P2/c space group. In morphological aspects, the control sample's wolframite structure has slight morphological deformations whereas the 200-shocked sample has an almost ideal morphology of the wolframite structure. Optical property results demonstrate a slight enhancement of the optical transmittance in the UV–Visible and NIR regions along with a blue shift at the 200-shocked condition. The above-mentioned analytical results reveal that the applied shock waves have effectively induced the thermal softening process, reducing the lattice and surface stresses on the test sample. A detailed discussion on the triangle relation of the structure-morphology-property of the control and shocked samples is provided.

Numerical investigation of infragravity wave hydrodynamics at fringing reef with a permeable layer

In tropical and subtropical coastal regions, coral reefs are abundant and play a vital role in maintaining ecosystem balance. Additionally, they effectively dissipate a significant amount of wave energy that propagates from the open sea towards the coastline, providing coastal areas with protection against wave impacts. Consequently, numerous scholars have conducted extensive research to investigate the hydrodynamic characteristics of wave propagation and transformation over coral reef topography. However, previous studies have often simplified the bottom boundary of coral reefs as impermeable layers, neglecting the fact that the coral reef consists of a permeable canopy structure in the actual marine environment. To fill the knowledge gap of previous research, this study is based on the Non-Hydrostatic Wave Model Solver (NHWAVE) to numerically simulate the propagation process of random waves over permeable coral fringing reefs. The study takes a comprehensive approach by considering the influences of various factors on the hydrodynamic characteristics of random waves over the fringing reef, including incident wave height, reef-flat water depth, peak wave period, permeable layer thickness, permeable layer porosity, and median diameter of the permeable layer. This paper focuses primarily on analyzing the variations in sea-swell wave height (HSS), infragravity wave height (HIG), and mean water level (MWL) along the fringing reef, while conducting a comparative analysis between fringing reefs with a permeable layer and impermeable fringing reefs. The findings reveal that the presence of a permeable layer reduces the shallow water deformation of waves on the fore-reef slope and mitigates the wave-breaking phenomenon near the reef edge, thereby significantly reducing the sea-swell wave height (HSS), infragravity wave height (HIG), and wave setup on the reef-flat. Furthermore, the permeable layer's existence also leads to a decrease in the maximum wave run-up height on the back-reef slope. The research findings of this study can further enhance our understanding of the hydrodynamic characteristics of infragravity waves over fringing reefs, which is significant for studying the impact of random waves on coastal areas and understanding the protective mechanisms of coral reefs in coastal regions.

Field measurements of aerodynamic pressures induced by suburban rail transit train passing through double-track tunnel with mid-partition wall

ABSTRACT Suburban rail lines, which provide fast connections between city centre and the surrounding suburbs, are attracting more and more attention from cities. As a train passes through the tunnel quickly, it tends to produce significant aerodynamic effects. In this study, a series of field measurement experiments were carried out in two tunnels with the mid-partition wall. The influence of train speed and tunnel length on the aerodynamic pressure was analysed. The aerodynamic pressure in adjacent tunnel was also discussed. Furthermore, the attenuation law and coefficient of aerodynamic pressure in tunnels with mid-partition walls were discussed. On this basis, a theoretical calculation model for predicting the peak positive pressure inside tunnels with different lengths and attenuation characteristics was established. The results show that the tunnel length not only affects the amplitude of the pressure, but also significantly affects the distribution trend of the pressure peak in the longitudinal direction. The propagation and reflection processes of pressure waves also exist in the adjacent tunnel on the other side of the partition, and they are synchronous. For the horse-shaped tunnel with mid-partition walls, the peak pressure inside the tunnel is directly proportional to the 2.05–2.20 power of the train speed, and the peak pressure decays exponentially with time. The pressure attenuation coefficient is greatly influenced by the placement of the measuring point, ranging from 4.957 × 10 − 5 to 8.184 × 10 − 5 depending on the position of the measurement point. This work provides important data support for studying the tunnel aerodynamic effects and verifying related numerical simulations.