Wave Action Research Articles

Morphological evolution of the Qingshuigou subaqueous delta of the Yellow River before and after the operation of the Xiaolangdi Reservoir (1997-2007)

The Modern Yellow River Delta has a rich history of geomorphological transformations shaped by frequent avulsions and rapid progradation. However, the delta entered a phase of altered morphodynamics following the construction of the Xiaolangdi Reservoir, which fundamentally restructured sediment transport regimes and seasonal hydrological patterns. These changes have amplified challenges in predicting long-term deltaic evolution under evolving boundary conditions. The Qingshuigou Subaqueous Delta, as a major depositional zone, provides a compelling lens to examine these morphodynamic processes. However, seasonal variations in riverine sand transport fluxes driven by the water-sand regulation scheme that accompanied the construction of the Xiaolangdi Reservoir and its impact on the evolution of the delta front are particularly understudied. This study developed a simplified long-term morphodynamic model of the Qingshuigou Subaqueous Delta to investigate its response to riverine water and sediment discharges from 1997 to 2007. The findings are as follows: (1) The morphological evolution of the Qingshuigou Subaqueous delta has gradually changed from the pattern of “leading edge deposition and localized near-shore erosion” before the construction of the Xiaolangdi Reservoir to the pattern of “enhanced leading edge deposition and increased near-shore erosion” after the construction. (2) The construction of Xiaolangdi Reservoir has weakened the spatial distribution of the erosion process to a certain extent, changing the spatial distribution dominated by the erosion process (63.8% of area) before the construction to the spatial distribution dominated by the accretion process (More than 50% of area) after the construction. (3) The spatial and temporal variability of the incoming sediments leads to a significant coarsening of the grain size of the tidal flats in the southern part of the abandoned delta, which in turn maintains a relatively steady state of the shoreline variability. In contrast, the abandoned sand spit experiences severe erosion and depositional fluctuations due to intensified wave action. (4) The study emphasizes the importance of considering seasonal variations in unsteady discharge in modeling the long-term evolution of the delta. It provides new insights into the spatial and temporal differentiation of the geomorphic equilibrium of the Yellow River Delta and contributes to a broader understanding of delta evolution.

Threshold for oscillatory-flow ripple initiation on cohesive and non-cohesive mixtures of sand and mud

ABSTRACT The threshold hydraulic condition of wave ripple initiation has been essential in a wide range of disciplines, including coastal engineering and geology, but remains unclear for the case of sand-mud mixtures as substrates. Scale experiments were conducted using an oscillating-bed to study wave ripple initiation in sand-mud mixtures, considering bed material, wave period and maximum orbital velocity. Four kinds of sand-mud mixtures were employed as bed material with different muds (cohesive kaolin and non-cohesive silt) and mixing ratios. Ripple initiation in the cases with sand-mud mixtures tended to require larger orbital velocity than pure sand, indicating that mud mixed in bed material hinders ripple formation and spreading of the ripple field. The results of the threshold for pure sand and 10% kaolin mixture show that cohesive mixed sand-mud hindered ripple formation and spreading. In contrast, in the case of the non-cohesive sand-silt mixture beds, the results differed depending on the proportion of sand and silt, which implied the effect of the strength of network structure. The inhibition of ripple initiation due to mud mixing observed in the present experiments is considered to have a significant effect, particularly in environments with limited wave action duration, such as intertidal zone.

MODELING THE DEFORMATION PROCESS OF AN UNDERWATER GAS PIPELINE UNDER THE EXPLOSIVE LOADING

The process of deformation of an underwater two-layer gas pipeline during the explosion of a nearby octogen charge is simulated. For modeling, a specially developed proprietary software package is used to solve three-dimensional dynamic problems of interaction of elastoplastic structures with compressible media, based on a single Godunov scheme of increased accuracy for calculating the joint motion of gas, liquid, and elastoplastic media. The package uses an Eulerian-Lagrangian approach with explicit identification of moving contact surfaces between different media. For each environment, three types of computational grids are used. These are Lagrangian surface meshes in the form of a continuous set of triangles for specifying the initial geometry of bodies and accompanying them during the calculation process, as well as two types of three-dimensional volumetric meshes automatically generated during the calculation process. The charge, which has a spherical shape, is initiated at its center. To describe the process of propagation of steady-state detonation, the hydrodynamic theory of detonation is used. Shock waves generated during an explosion in the surrounding liquid interact with a fragment of a two-layer pipeline and a solid bottom. Wave processes are analyzed both in the steel pipe and in the concrete shell that weighs it down. Loads on the pipeline are estimated depending on the distance to the charge and the position of the pipeline relative to the bottom. The possible destruction of both steel and concrete weight shells in areas of tensile deformations that are formed in places of the maximum bending of the pipeline is shown. It is shown that the proximity of the bottom can significantly enhance the impact of explosive loading due to the action of shock waves reflected from the bottom.

Numerical Simulation of Wave-Induced Scour in Front of Vertical and Inclined Breakwaters

The erosion of the seabed in front of shoreline structures due to wave action is a critical concern. While previous models accurately depict fluid and sediment interactions, they each have limitations and require significant computational resources, especially when simulating complex processes. This study proposed and validated a numerical model for simulating wave-induced sediment transport by integrating three key components: (1) a main solver based on large eddy simulation that includes the porosity of permeable materials, (2) a volume of fluid module to track the air–water surface, and (3) a sediment transport module that includes both bedload and suspended load to compute sediment concentrations and seabed changes. The model was validated against previously published experimental data, demonstrating its accuracy in capturing both wave motion and seabed profile changes induced by sediment transport. Furthermore, the numerical model was applied to study the effects of varying breakwater slopes on sediment seabed profile changes. The results show that steeper breaker slopes led to more concentrated wave energy near the structure, resulting in deeper scouring and higher sediment displacement. These results indicate that the proposed model is a valuable tool for coastal engineering applications, particularly for designing breakwaters, to mitigate sediment erosion and improve sediment stability.

Analytical solution for single pile in two-layered soil subjected to torsion

ABSTRACT Pile foundations are often used to support large structures including wide and high commercial buildings, offshore and onshore structures, bridges and transport corridors (railways and highways). Apart from usual vertical loading from superstructures, these piles are subjected to lateral loading because of the actions of waves, ship impacts or moving vehicles. Eccentricity of such lateral load initiates torsion pile producing twist and interface horizontal shear stress on the piles. Although there are several theoretical solutions (analytical/numerical) available for torsionally loaded piles, appropriate model on the response of single pile in layered soil under torsion is limited. The current paper presents a simplified analytical model based on limit state analysis to study the response of single pile in two-layered soil subjected to pure torsion. The solution developed is validated by comparison with available field test data on a pile with torsional load. Using the model, extensive parametric studies have been carried out on single pile under torsional load embedded in two-layered soil, both clay overlying sand and vice versa. A set of design curves representing the ultimate torsional capacity and ultimate angle of twist are developed which can be beneficial and convenient for practicing engineers.

Physics-guided deep learning for skillful wind-wave modeling.

Modeling sea surface wind-waves is crucial for both scientific research and engineering applications. Nowadays, the most accurate wave models are based on numerical methods, which primarily concern the wave spectrum evolution by solving wave action balance partial differential equations. These methods are computationally expensive and limited by incomplete physical representations of wave spectral evolution. Here, we present a deep learning-based wave model trained using observation-merged wave hindcasts. Guided by the physics knowledge that waves are either generated by local current winds or by remote historical winds, this method can directly model significant wave height, bypassing the need for wave spectral information. This feature engineering effectively reduces the complexity of model inputs and outputs. The resulting artificial intelligence method can model 1 year of global significant wave heights at a 0.5° × 0.5° × 1-hour resolution within half an hour on a personal computer, achieving higher accuracy than state-of-the-art numerical wave models.

Shaking Table Test of Dynamic Response of Near-fault Rock-embedded Pile Foundation Under Strong Seismic Action

Dynamic response characteristics of near-fault bridge pile foundations under seismic wave action are studied by using a large shaking table model test. The results show that the peak acceleration at the top of the pile is more significant than that at the bottom. The pile top acceleration response is most significant for the EI-Centro wave and least significant for the 5002 wave. The maximum values of the permanent horizontal displacement of the pile top and the permanent relative horizontal displacement between the pile tops of the upper and lower plate piles appear under the action of the Kobe wave. The maximum pile bending moment appears to be at the interface of the upper overburden layer and the interface of the lower bedrock and overburden layer. The amplification coefficient of the pile top acceleration, the peak horizontal displacement of the pile top and the peak bending moment of the pile body of the upper plate pile foundation are more significant than those of the lower plate.

Quantification of Nearshore Sandbar Seasonal Evolution Based on Drone Pseudo-Bathymetry Time-Lapse Data

Nearshore sandbars are dynamic features that characterize shallow morphobathymetry and vary over a wide range of geometries and temporal lifespans. Nearshore sandbars influence beach geometry by altering the energy of incoming waves; thus, monitoring the evolution of sandbars is a fundamental approach in effective coastal planning. Due to several natural and technical limitations related to shallow seafloor mapping, there is a significant gap in the availability of high-resolution, shallow bathymetric data for monitoring the dynamic behaviour of nearshore sandbars effectively. This study introduces a novel image-processing technique that produces time series of pseudo-bathymetric data by utilizing multi-temporal (monthly) drone imagery, and it provides an assessment of local morphodynamics at a sandy beach in the southeast Mediterranean. The technique is called standardized-ratio bathymetric index (SRBI), and it transforms natural-colour drone imagery to pseudo-bathymetric data by applying an empirical formula used for satellite-derived bathymetry. This technique correlates well with laser altimetry depth measurements; however, it does not require in situ depth data for implementation. The resulting pseudo-bathymetric data allows for extracting cross-shore profiles and delineating the sandbar crest with 4 m horizontal accuracy. Stacking of temporal profiles allowed for the quantification of the sandbar’s crest and trough changes at different alongshore sections. The main findings suggest that the nearshore crescentic sandbar at Episkopi Beach (north Crete) shows strong seasonality regarding net offshore migration that is promoted by enhanced wave action during winter months. In addition, the crescentic sandbar is susceptible to morphology arrestment during prolonged weeks of low wave action. The average migration rate during winter is 10 m.month−1, with some sections exhibiting a maximum of 60 m.month−1. This study (a) offers a novel remote-sensing approach, suitable for nearshore seafloor monitoring with low computational complexity, (b) reveals sandbar geometry and temporal change in superior detail compared to other observational methods, and (c) advances knowledge about nearshore sandbar monitoring in the Mediterranean region.

Numerical examination of wave forces on partially submerged horizontal circular cylinders near free surface

Determining wave forces on partially submerged horizontal circular cylinders near free surface is a significant issue. This study explores hydrodynamic coefficients and wave forces on horizontal circular cylinders near free surface under large-amplitude wave actions using a viscous fluid numerical wave tank model based on the finite volume method, with a particular aim to accurately predicting the slamming force. By analyzing the characteristics of the wave forces and slamming forces on the circular cylinder, the influences of wave amplitude, wave frequency and vertical position of the cylinder on the wave forces are investigated, and the relationships between the slamming forces and fluid velocity are discussed. Additionally, a modified Morison's equation for predicting the wave forces is derived considering the slamming force and the condition of the circular cylinder completely exposed to the air phase under the action of large-amplitude wave. The results of this study reveal that the wave forces on the circular cylinder are significantly influenced by wave amplitude, frequency and vertical position of the cylinder, and the influences of the cylinder position on the predicted minimum slamming velocity are remarkable. The present study demonstrates that modified Morison's equation is plausible and accurate in predicting the wave and slamming forces for submerged or floating structures.

An Investigation of Silty Sediment Erodibility Considering the Effects of Upward Seepage and Slope Gradient

The phenomenon of extensive erosion of silty submarine slopes in the Yellow River delta has been well documented in numerous studies. Due to poor drainage and high compressibility, silty sediments are particularly prone to pore pressure buildup and accumulated seepage under wave and current action, which can influence sediment erodibility (e.g., the critical bed shear stress and the erosion rate under various bed shear stresses). To date, there remains a lack of parametric formulation to quantitatively characterize the erodibility of silty sediments with the coupled effects of the hydraulic gradient of upward seepage and the slope gradient. In this study, a series of laboratory experiments were conducted to explore the erodibility of silt sediments from the Yellow River delta under varying hydraulic gradients of upward seepage and slope gradients. The results reveal that both upward seepage and increased slope gradients can enhance the erodibility of silty sediments. Specifically, as the seepage gradient increases from 0.1 to 0.8, the critical Shields parameter required for initiating silty particle motion decreases linearly, with a reduction rate of 0.01 per 0.1 increase in the seepage gradient, independently of changes in slope gradient. Additionally, the erosion coefficient of silty sediments grows exponentially with rising seepage gradients, with its average growth rate accelerating with increasing slope inclination. For flat sediment beds, the erosion coefficient influenced by upward seepage can be up to five times that in the absence of seepage. An empirical formula for calculating the critical Shields parameter and an erosion model incorporating upward seepage gradient and slope effects were developed through multiple regression analysis, providing an experimental basis for numerical simulations of scour in silty submarine slopes under combined waves and currents.

Co-Occurrence Patterns of Aquatic Macroinvertebrates in Laurentian Great Lakes Coastal Wetlands.

In niche-based community assembly theory, it is presumed that communities in habitats with high natural disturbance regimes are less likely to be structured by competitive mechanisms. Laurentian Great Lakes (hereafter Great Lakes) coastal wetlands can experience drastic diel fluctuations in dissolved oxygen levels, severe wave action, ice scour, and near complete freezing during the winter such that conditions are inhospitable for most organisms. The high natural disturbance levels are thought to cause high interannual turnover for aquatic macroinvertebrate communities and support the hypothesis that these communities are less likely to experience less competitive interactions and negative co-occurrence structure. We hypothesize that non-random co-occurrence patterns will be rare in Great Lake coastal wetlands and non-competitive processes (e.g., through shared or differential microhabitat affinities, pollution tolerances, or biotic homogenization) will be more common than competitively driven negative co-occurrence patterns. Null model analysis was performed on 134 macroinvertebrate communities sampled from across the Great Lakes basin from 2000 to 2013. To disentangle the effects of alternative structuring mechanisms (i.e., shared/differential habitat affinities, shared/differential pollution tolerance, and biological homogenization/competitive exclusion), communities were parsed based on the year sampled, the vegetation type from which community samples were collected, and lastly species' functional feeding group assignment or taxonomic group. As expected, very few communities were non-randomly structured; however, all of those that were non-random exhibited showed more negative co-occurrences than by chance. Upon further investigation, these communities consisted of species that are known to overwinter in wetlands, and therefore, avoid having to recolonize after each spring thaw. With expected changes in habitat conditions due to climate change, we propose that null model analyses can be used as an early warning system for community change.

Numerical and experimental study on local scour in front of OWC-BWS under waves

In this paper, a system of an oscillating water column wave energy converter integrated with a vertical breakwater (OWC- BWS) was established, and the scour mechanism in front of OWC-BWS under wave actions was studied by laboratory scale experiments and gas-liquid-particle flow numerical simulation, respectively. The experiment investigates the comparison of scour test results between a conventional vertical breakwater and OWC-BWS. It shows that compared to a vertical breakwater without an OWC, the local scour phenomenon in front of the OWC-BWS was effectively mitigated (test results showed a 46.7% reduction in the maximum scour depth). For numerical simulation, a scour model under wave actions was established for further research on the local scour mechanism in front of the OWC-BWS. It was found that the local scour topography of an OWC-BWS is different from that of a vertical breakwater. The OWC device effectively weakens the scour in front of the OWC-BWS, which is because the flow field in front of the OWC-BWS shows frequent generation and shedding of vortexes. In addition, as a crucial part of the OWC-BWS, the effect of PTO was also studied, which found that the maximum equilibrium scour depth was significantly influenced under different PTO.

Transport and deposition of terrestrial organic matter in marine littoral deltas: New evidence from flume experiments and 3D laser scanning

Terrestrial organic matter (TOM) serves as the primary parent material for source rocks in marine-terrestrial transitional environments. The transport and deposition process of TOM affects the development of high-quality source rocks in shallow marine areas. Based on the sequence stratigraphy of the Enping Formation (upper Eocene to lower Oligocene) in the Baiyun Sag and the petrological characteristics of the source rocks, simulation experiments of terrestrial dispersed organic matter deposition constrained by topography, provenance composition, sedimentation period and other conditions were conducted. Comparative experiments of individual constraints such as topographic slope, hydrodynamic conditions, water salinity and particle size of organic matter were also conducted. The results indicate that TOM enrichment in the littoral delta system initially increases with transport distance but subsequently decreases. Four TOM distribution patterns were identified: interrupted, interbedded, lenticular, and banded types. The interrupted, interbedded, and lenticular types predominantly occur in delta plains, whereas the banded type primarily develops in delta fronts and prodeltas. In the early stages of delta formation, gentle slope conditions are more conducive to the forward transport of TOM. As the delta develops, the sediment thickness increases, which reduces the slope gradient and thus weakens the effect on the transport distance of TOM. Higher flow intensity promotes TOM transport, however, wave action can impede forward transport, creating localized TOM enrichment areas on the delta plain. In shallow water, the increase in water salinity enhances the flocculation of TOM, thus reducing the transport distance of TOM. Meanwhile, Smaller TOM particle sizes correspond to greater transport distances and increased heterogeneity in its planar distribution within the delta-shallow sea sedimentary system.

Influence of Rocking Shallow Foundation Parameters and Analysis of Seismic Response Characteristics

Rocking shallow foundations interrupt the seismic transmission path from the base of the structure and possess advantages, such as effective seismic isolation, self-resetting capabilities post-earthquake, and low costs. A numerical model of the rocking shallow foundation was developed in OpenSees (version: Opensees 3.5.0) based on field test data using numerical simulation. The effect of different parameters (column height, foundation sizes, top mass, and soil softness and stiffness) on the seismic response characteristics of rocking shallow foundations is investigated, and the seismic response characteristics of rocking shallow foundations are analyzed under the action of sinusoidal waves of different frequencies and various seismic wave types. The results of the study show that, as the height of the column increases, the bending moment decreases and settlement decreases; as the size of the foundation increases, the bending moment increases and settlement increases; as the mass of the top increases, the bending moment increases and settlement increases; and as the soil becomes softer, the bending moment decreases, and settlement increases. Inputting a sine wave that matches the structure’s natural oscillation frequency may induce resonance. This phenomenon can significantly amplify the structure’s vibrations; thus, it is essential to avoid external excitation frequencies that coincide with the foundation’s natural oscillation frequency. Under seismic loading, the rocking shallow foundation can mitigate the bending moment in the superstructure. When the displacement ratio remains within −0.5 to 0.5 percent, the foundation settlement is minimal. However, when the absolute displacement ratio exceeds 0.5 percent, the soil exhibits plastic deformation characteristics, resulting in increased foundation settlement. This study is an important contribution to the improvement of seismic performance of buildings and an important reference for improving seismic design standards and practices for buildings in earthquake-prone areas. In the future, the seismic response characteristics of rocking shallow foundations under bidirectional seismic action will be investigated.

Modal Parameter Identification of Jacket-Type Offshore Wind Turbines Under Operating Conditions

Operational modal analysis (OMA) is essential for long-term health monitoring of offshore wind turbines (OWTs), helping identifying changes in structural dynamic characteristics. OMA has been applied under parked or idle states for OWTs, assuming a linear and time-invariant dynamic system subjected to white noise excitations. The impact of complex operating environmental conditions on structural modal identification therefore requires systematic investigation. This paper studies the applicability of OMA based on covariance-driven stochastic subspace identification (SSI-COV) under various non-white noise excitations, using a DTU 10 MW jacket OWT model as a basis for a case study. Then, a scaled (1:75) 10 MW jacket OWT model test is used for the verification. For pure wave conditions, it is found that accurate identification for the first and second FA/SS modes can be achieved with significant wave energy. Under pure wind excitations, the unsteady servo control behavior leads to significant identification errors. The combined wind and wave actions further complicate the picture, leading to more scattered identification errors. The SSI-COV based modal identification method is suggested to be reliably applied for wind speeds larger than the rated speed and with sufficient wave energy. In addition, this method is found to perform better with larger misalignment of wind and wave directions. This study provides valuable insights in relation to the engineering applications of in situ modal identification techniques under operating conditions in real OWT projects.

Hydrodynamic Characteristics of Offshore Wind Turbine Pile Foundations Under Combined Focusing Wave-Current Conditions

In extreme marine environments, the interaction between offshore wind turbine pile foundations (OWTPFs) is critical, and the associated hydrodynamic loads are complex. This study focused on fixed OWTPFs and used computational fluid dynamics (CFD) to numerically simulate the flow field around pile foundations under the combined action of focusing waves and current. The objective was to investigate the influence of different focusing wave and current parameters on the hydrodynamic properties of the pile foundations. The findings indicate the following: (1) When the wave and current directions are opposite, the maximum wave force on the pile foundations is greater than when they are aligned. (2) Large-amplitude focusing waves around pile foundations generate secondary loads, which are nonlinear and lead to a rapid increase in the wave force. These secondary loads are short-lived and particularly prominent near the front row of pile foundations. (3) The influence of the group pile effect diminishes under high-amplitude waves, where the wave component dominates the generation of the dimensionless wave force, and the impact of the current on this force decreases.

Experimental study on heat transfer and resistance of round tube with tube sheet under ultrasonic action

AbstractEnergy is vital to the survival and development of human beings. In the era of ‘carbon neutrality’, all walks of life around the world are upgrading their technological capabilities to reduce carbon emissions. As a new type of active strengthening technology to improve the comprehensive performance of heat exchangers, ultrasonic technology has attracted the attention of more and more scholars. From the actual installation situation, a set of ultrasonic enhanced heat transfer test device with tube sheet round tube was built. After experimental research and data analysis, the influence of ultrasonic sound intensity, frequency, and position on heat transfer, flow resistance, and comprehensive performance of heat exchange tube under different working conditions and without ultrasonic wave is studied. The results show that the ultrasonic enhanced heat transfer and drag reduction capacity increases with the decrease of ultrasonic frequency, and under the action of ultrasonic waves of different frequencies, the critical sound intensity of its enhanced heat transfer and drag reduction performance is different. The drag reduction performance of the ultrasonic heat exchange tube is increased by 18.41%, the heat transfer performance is increased by 36.53%, and the overall performance is increased by 20.57%.

Short-stasis signatures in Cambrian and Ordovician shallow-marine sandstones: Implications for the ichnological record and time preserved at outcrop

Shallow-marine sandstones are an archetypal facies in the stratigraphic record of the Cambrian Explosion and the Ordovician Radiation but have been considered uninformative due to erosional signatures, time-incompleteness, and unfossiliferous outcrops. New analyses of the Carnedd-y-Filliast Grits (Furongian, Wales) and littoral sandstone successions from Laurentia and Baltica reveal that bedding planes in such outcrops commonly register sedimentary stasis. Most stasis intervals were brief, reflecting 1) a high sedimentation frequency; 2) post-depositional substrate resculpting by wave action during ‘active-layer stasis’, inhibiting infaunal colonization and rendering the surface representative of only the interval immediately preceding burial; and 3) the low preservation-potential of longer-stasis surfaces, which mainly occur within heterolithic packages that, in low-subsidence settings, are commonly eroded and replaced by amalgamation surfaces between sandstones. The short-stasis signature of littoral sandstones renders meter-scale architectural elements relatively time-complete but biases their fossil record at outcrop. Short-stasis surfaces are high-resolution snapshots but form incomplete representations of ancient ecosystems compared to surfaces that capture longer intervals. As such, the predominance of short-stasis surfaces contributed to the low ichnodiversity and sparse fossil content of littoral sandstones, implying that early Palaeozoic littoral ecosystems were more biodiverse than their known record suggests.

Dynamic response analysis of a floating bridge structure under combined actions from seismic loading and waves at different incident angles

Abstract This paper investigates the complex coupled response of a cross-sea floating bridge under the combined actions of seismic loading and wave at different incident angles. The bridge structure is modeled using the finite element method, considering the interaction between the girder, pier, pontoon, and mooring chains. Wave forces are calculated based on potential theory, and an added mass approach is applied to simulate the hydrodynamic forces induced by the earthquake. Simulations were conducted using a one-year random wave at three different incident angles of 0o, 45o, and 90o, combined with three-dimensional seismic loading of varying magnitudes: 0.3 g, 0.5 g, and 1 g. The simulation results indicate that the direction of the incident wave significantly influences the bridge's response. The coupling effect between wave and seismic forces on the floating bridge's response is not simply additive. Generally, when the earthquake magnitude is low, the wave loading significantly impacts the bridge's dynamics. However, as the earthquake magnitude increases, the bridge's response becomes dominated by the seismic forces, rendering the influence of wave forces negligible.

Unsteady phenomena in the exhaust circuit of turbocharged automotive engines

Abstract The application of turbocharging is still a crucial aspect, especially in hydrogen engines where ultra-lean combustion is required, to mitigate abnormal combustion and NOx formation. The adoption of advanced turbocharging systems results in an increased complexity of the engine intake and exhaust circuits and requires a proper design to optimize unsteady flow phenomena. Therefore, it is essential to understand the performance of the single elements of the turbocharging circuit and their interactions when coupled. A specific test rig for components of propulsion system is operating at the University of Genoa, where investigations under steady, transient and pulsating flow conditions can be performed. This study presents the results of experimental investigations conducted under unsteady flow conditions on the exhaust manifold of an internal combustion engine, specifically examining unsteady phenomena in the turbine inlet circuit. The pulsating flow is generated by a motor-driven cylinder head. Pressure signals recorded in different sections of the exhaust circuit located in the inlet and outlet turbine circuit are analysed in detail, quantifying also the effects of flow unsteadiness using parameters proposed in the open literature. In particular in the following article, the degree of instability, the Strouhal number and the reduced frequency are considered to quantify the impact of unsteady phenomena within the system for the considered lengths. Understanding the unsteadiness within engine circuits is crucial for determining the appropriate modeling approach for system simulation. This work highlights that a quasi-steady flow model is appropriate for modeling individual branches for the exhaust manifold, while a wave action model is necessary for the entire exhaust circuit.