Use Of Hydrodynamic Model Research Articles

On the use of hydrodynamic modelling and random forest classifiers for the prediction of hypoxia in coastal lagoons

Hypoxia is one of the fundamental threats to water quality globally, particularly for partially enclosed basins with limited water renewal, such as coastal lagoons. This work proposes the combined use of a machine learning technique, field observations, and data derived from a hydrodynamic and heat exchange numerical model to predict, and forecast up to 10 days in advance, the occurrence of hypoxia in a eutrophic coastal lagoon. The random forest machine learning algorithm is used, training and validating a set of models to classify dissolved oxygen levels in the lagoon. The Orbetello lagoon, in the central Mediterranean Sea (Italy), has provided a test case for assessing the reliability of the proposed methodology. Results proved that the methodology is effective in providing a reliable short-term evaluation of DO levels, with a high resolution in both time and space throughout an entire lagoon. An overall classification accuracy of up to 91 % was found in the models, with a score for identifying the occurrence of severe hypoxia - i.e. hourly DO levels lower than 2 mg/l - of 86 %. The use of predictors extracted from a numerical hydrodynamic model allows us to overcome the intrinsic limitation of machine learning modelling approaches which rely on input data from relatively few, local field measurements, i.e. the inability to capture the spatial heterogeneity of DO distributions, unless several measuring points are available. The methodological approach is proposed for application to similar eutrophic environments.

Integration of empirical and modelled data unravels spatiotemporal distribution and connectivity patterns of Fuegian sprat early life stages

The distribution patterns of fish early life stages are critical to recruitment success and closely related to major oceanographic circulation patterns. We explored the spatiotemporal distribution of early life stages of Fuegian sprat Sprattus fuegensis, a key trophic species in the Southwestern Atlantic Ocean (SWAO), in a complex oceanographic setting. Samples were collected during austral spring, summer, and autumn, from 2014 to 2017, across areas with distinct biophysical properties between Tierra del Fuego (TDF) and the marine protected area ‘Namuncurá’ at Burdwood Bank (BB) (ca. 54°S). Results revealed significant seasonal fluctuations in abundance, distribution, and ontogenetic composition across habitats. High egg and early larval abundances at Isla de los Estados (IE) suggest it is an additional spawning ground to those previously identified at TDF and BB. However, only the latter appear to be suitable nursery areas. Particle-tracking simulations based on egg abundance and spawning dates were conducted for the first time using results from a high-resolution hydrodynamic model. Particle transport provides evidence of connectivity between IE and neighbouring areas—enhanced when horizontal diffusivity is incorporated into the model—but not between TDF and BB. Simulated distributions closely resembled empirical patterns from this and other studies, allowing the integration of empirical and modelled data to schematize the species’ dispersal pathways in the study area. These results offer new insights into distribution and connectivity patterns among spawning grounds and highlight the potential use of hydrodynamic models for future assessments of Fuegian sprat and other planktonic species’ dispersal and recruitment in the SWAO.

Assessment of the Feasibility of Implementing a Flash Flood Early Warning System in a Small Catchment Area

The occurrence of flash floods is an increasingly common phenomenon. In many parts of the world, it is associated with an increase in the intensity of rainfall. Reducing the financial and social losses caused by the occurrence of local urban floods is possible through the use of hydrodynamic modeling and real-time flood forecasting. The purpose of this study is to assess the ability of the modeling technique to simulate the flow in a small catchment area and to determine the time remaining to reach the set warning and danger levels. SWMM 5.2 and QuantumGIS software were used in the study. The analysis showed that for the considered catchment area with a short length of the main stream (1612 m), the time possible for implementing countermeasures and evacuating the population is 70 to 120 min. The study also confirmed that short-term rainfall requires less depth to reach high stormwater elevations than long-term rainfall. In addition, a relationship was noted between the preceding rainfall and the height of stormwater and the forecast time. There was an unfavorable reduction in forecasting time as the depth of rainfall increased and its duration shortened. In the case of the analyzed catchment, the maximum elevation of stormwater (Esw,max) is generated by rainfall that is characterized by the highest intensity in the final phase of their duration. Similarly, the longest forecast time (tf) for the maximum stormwater elevation is caused by rainfall, which is characterized by the highest intensity in its final phase. The results of the study can significantly assist local governments when developing a catchment management plan and when trying to implement practices to minimize the negative effects of flash floods.

Implementation of the AdH hydrodynamic model on the Włocławek Reservoir

The variation of water velocity in an artificial dam reservoir is influenced not only by the inflow discharge, but also by the bathymetry of the reservoir and the water level at the dam. The depiction of spatially complex variations in flow velocity through a reservoir would not be possible without the use of hydrodynamic models. A reliable hydrodynamic model of the reservoir is an effective tool for predicting and analyzing changes in the reservoir geoecosystem in an age of changing climate and risk of water stress. A depth-averaged two-dimensional AdH model was used to visualize the hydrodynamics of the Włocławek Reservoir. Running the model for eight different hydrological conditions delivered consistent results and allowed to calibrate the model parameters. Additionally, it provided a way to verify the data regarding the rating curve of the Vistula River upstream the reservoir.

Повышение выработки запасов конденсата методом периодических остановок скважин

Introduction. During the development of gas condensate deposits for depletion, with a decrease in reservoir pressure, condensate falls out in the bottomhole zone of wells (BWZ) and a zone with increased condensate saturation is formed. Materials and methods of research. The considered method of non-stationary operating mode was justified by the example of the development of the Achimov deposits of the Urengoyskoye field using the tNavigator software package. Research results and their discussion. The work studies a method of periodical shutting down a gas condensate well in order to increase the additional recovery of retrograde condensate from the reservoir. The optimal well shutdown period is substantiated through the use of hydrodynamic modeling. The paper also analyzes the factors aimed at maintaining the maximum effect from the periodic operation of the well, the main of which is the mode of operation after the well is launched. The considered method of non-stationary operating mode was justified by the example of the development of the Achimov deposits of the Urengoyskoye field using the tNavigator software package. The initial information for modeling was the following: monthly operational reports (MER); results of gas condensate studies; downhole and wellhead measurement data. Conclusion. Based on the studies performed to determine the optimal duration of well shutdown during the development of the Achimov deposits of the Urengoyskoye field, it was revealed that the shutdown duration (more than 183 days) will have a negative impact on the potential condensate content in the formation gas. It has been substantiated that the efficiency of periodic shutdowns is affected by the technological mode of well operation after start-up. Also, the drawdown reduction makes it possible to preserve the effect of the reverse dissolution of condensate through the use of the natural energy of the reservoir.

Seaweed dispersion under different environmental scenarios based on branches settling velocity and hydrodynamic lagrangian model

We examined the spatial pattern of seaweed branches dispersion based on lagrangian numerical simulation of an experimental cultivation of the seaweed Kappaphycus alvarezii. Sambaqui Beach seaweed cultivation located in the Bay of Santa Catarina Island southern Brazil was used as case study. This work is the first step towards understanding the dispersion and the range of detached branches in the estuarine region. For that, the use of hydrodynamic modeling as tool to support the evaluation of the water dynamics and particles fate was considered. Several environmental datasets are needed as input for hydrodynamic mathematical models, like bathymetry, tide time series, and branches settling velocity. The experiments on branches vertical velocities, in this study, varied from 3.2 until 5.7 cm.s−1, which presented a high correlation with branches volume. These velocities associated with the hydrodynamic model resulted that 90% of the branches will disperse to an area varying from 2 to 6 ha depending on the simulated scenario. Besides, model results shows that particles traveled distances up to 2.5 km, but most of them did not reach the coastline. Although the need for a large amount of data and numerical modeling effort, the results show that this type of approach can reduce the monitoring area around 75% and consequently reduce the need for human resources, time, and inputs in monitoring the dispersion of branches of exotic seaweed in the environment.

NEW METHOD FOR SPLITTING PRODUCTION AND INJECTION IN JOINT WELLS USING MODIFIED CRM MODEL

Operating several oil-bearing facilities with a single grid of wells, the problem of dividing oil and liquid production rates by facilities is urgent. Known engineering techniques based on reservoir transmissibility coefficients and effective oil-saturated thickness do not take into account dynamic factors. The use of hydrodynamic models (HDM) is time-consuming, and the results depend significantly on the used a priori hypotheses about the geological structure of objects and the properties of fluids. Thus, there is a practical need for an analytical tool that would rely on the most reliable and available data and would allow solving the problem of separating the volumes of produced fluid and injected water with sufficient accuracy. Such a tool should take into account the dynamics of changes in reservoir pressure and have a low (compared to the hydrodynamic model) need for computing resources. A promising candidate for the role of such a tool is the CRMP-ML6 model — a fundamentally new author’s modification of the previously known CRMP model. The CRMP model is a functional dependence of the well fluid flow rate on the injectivity of the surrounding injection wells. The unknown parameters of this dependence are determined in such a way as to minimize the discrepancy between the simulated and actual values of production rates at the selected date interval. Fundamentally new features of the CRMP-ML6 model are the regularization of the problem through the use of a priori information on the permeability of reservoirs in the vicinity of production wells and the requirement for the proximity of reservoir pressures calculated using the material balance model and from the Dupuis equation. To assess the performance of the new model, a number of numerical simulation experiments were carried out, and the simulation results were compared with the HDM. The possibility of the CRMP-ML6 model is demonstrated to take into account the dynamic separation of production and injection, taking into account additional constraints and a priori information, and while meeting all the requirements for models of the CRM family.

Sustainable process design for manufacturing acrylic acid from glycerol

Acrylic acid is a high-value monomer produced today only from petrochemical resources. This paper investigates the conceptual design of an eco-efficient process using renewable low-cost glycerol. The key step is glycerol dehydration to acrolein, performed in a fluidized bed reactor employing fast nanosheet zeolite catalyst. The investigation makes use of hydrodynamic modelling and computer simulation in Aspen Plus. The feasibility of four alternatives is studied: conventional bubble (BFB) and turbulent (TFB) fluidized bed, as well as two types of circulating fluidized bed (CFB) reactors. Working with smaller bubble size, in the range 2.5–10cm, a BFB reactor may achieve a productivity of 0.45kg/kg-cath for 99.7% conversion, which is only 20% of the performance of an ideal plug flow reactor. Changing to TFB regime raises the productivity to 0.9kg/kg-cath. Implementing CFB reactors leads to a spectacular improvement. High productivity of 3 and 4kg/kg-cath is achieved with turbulent (CTFB) and high-density (HD-CFB) reactors, respectively. The TFB reactor is preferred when catalyst coking is low or moderate, while CTFB is favoured when continuous regeneration is needed. Employing m-xylene driven azeotropic distillation leads to the lowest energy consumption reported so far by acrylic acid purification. The integration of reaction and separation sections by combined heat and power system leads to a positive energy process. Dynamic simulation demonstrates flexibility and robustness of the separation section faced with disturbances occurring in the reaction system. The sustainability indices show substantial improvement in eco-performance with respect to the propylene-based process.

Flood mapping employing local, regional and global scale modeling methods for the Uruguay river

The delimitation of flooded areas is important information for natural disaster management, environmental impact prediction and for territorial planning. Flooding occurs when water levels overflow the limits of a river’s channel and seep into the floodplains. When they affect people, they are considered a natural disaster. The delimitation of a flooded area, in the occurrence of an extreme event, can be performed by using field techniques, such as mapping, surveying through the afflicted area or by taking aerial photographs. However, field survey is not a trivial task and not always does it allow for the attainment of the necessary data for a given project. For that purpose, there are various techniques that can be used to assess flood-spots. Some techniques are simpler, being based only on a Digital Elevation Model (DEM), and such is the case of the HAND model (Height Above Nearest Drainage), which has garnered plenty of fame recently in the process of applying delimitations to possibly flooded areas. Other techniques are more complex, like the use of hydrodynamic modeling. There are large-scale hydrologic-hydrodynamic models that simulate runoff generation and water transportation processes in the river basin from rainfall, basin, and meteorological data. This is the case of the large-scale distributed hydrological model called MGB (Modelo de Grandes Bacias), which has been developed and employed in these types of cases. However, there are no studies in the literature that compare the results produced by these multiple approaches using differing degrees of complexity and spatial scales. It was precisely to fill this gap in scientific literature that this work was developed. Featured here, for the first time, is the validation of the MGB model’s performance in two versions, one of regional scale and another of continental scale (MGB AS), in delimiting the flooded areas, compared to a satellite image of the inundation; and with two versions of the HAND model, one generated by a local study and the other by a global reference. The case study used in this validation was a major flood that occurred in the Uruguay River, near the town of Itaqui (Rio Grande do Sul), which borders Brazil and Argentina, in October 1997. The results show that the MGB model, both in the regional and the continental scales, could delimit the flooded area, with a few overestimations in the northern portion of the image. The HAND method at the local scale also allowed a mapping of the flooded area, with overestimates for more springhead-like areas in small tributaries. The HAND method at the global scale, on the other hand, proved to be inadequate for the purpose of delimiting flooded areas in this region. The leading cause is believed to be the small drainage area threshold linked to the utilized global HAND product. From the calculation of performance metrics, like hit rate, false alarm ratio and criticality index, Regional MGB was the one that most adequately expressed the extent of the flood observed in the Landsat 5 image when compared to the others, followed by MGB AS.

Flood hazard analysis in small catchments: Comparison of hydrological and hydrodynamic approaches by the use of direct rainfall

AbstractThe classical ‘decoupled’ approach for fluvial flooding makes use of hydrographs as input boundary conditions. The catchment hydrology is determined by empirical semi‐distributed rainfall–runoff models, the flood processes by the use of hydrodynamic models. However, for urban floods, the distributed rainfall is set directly as input (‘direct rainfall modelling’ – DRM) to the elements of the 2D model. This ‘integrated approach’ aims to include hydrological and hydraulic processes in one single model. In this study, both modelling approaches are applied and evaluated for their suitability to determine flood hazards in small, rural catchments. The resulting flood maps and flow hydrographs are compared for selected rainfall–runoff events in a catchment located in Central Germany. In the first approach, the hydrological model (HEC‐HMS) from the Hydrologic Engineering Center (HEC) is used to generate the inflow boundary hydrographs for the 2D model (HEC‐RAS), which is then used to simulate the flow variables for the river network and its floodplains. For the second approach, the DRM is applied over the whole catchment by the use of HEC‐RAS. Special focus is given for the integrated approach to the difficulties occurring during the model optimisation and calibration. The comparison of the results and modelling processes of both approaches give insights into the advantages, disadvantages and difficulties or limitations of each presented approach.

Acoustical-phonon and polaron mode-induced optical parametric amplification in transversely magnetized III–V semiconductors

In this paper, a detailed analytical investigation is made to study the acoustical-phonon (AP) and polaron mode-induced optical parametric amplification (OPA) in transversely magnetized III–V semiconductors. Making use of hydrodynamic model of (one component) semiconductor plasma and adopting the coupled mode approach, an explicit expression is obtained for the threshold pump electric field [Formula: see text] and gain coefficients [Formula: see text] of AP and polaron mode-induced OPA. Externally applied magnetostatic field [Formula: see text] and doping concentration [Formula: see text] are incorporated in terms of electron cyclotron frequency [Formula: see text] and plasma frequency [Formula: see text], respectively. The dependence of [Formula: see text] on wave number [Formula: see text], [Formula: see text] and [Formula: see text] and the dependence of [Formula: see text] on [Formula: see text], [Formula: see text] and pump electric field [Formula: see text] are explored. Numerical estimates made for [Formula: see text]-InSb-CO2 system suggest that the material parameters and externally applied magnetostatic field play an important role in reducing [Formula: see text] and enhancing [Formula: see text]. We find [Formula: see text] (when [Formula: see text]); though [Formula: see text] is smaller than [Formula: see text] under identical conditions. The formulation developed in this paper highlights the importance of Frohlich interaction in transversely magnetized III–V semiconductors for OPA and replaces the conventional idea of using high power pulsed lasers. The results obtained in this analysis suggest that by controlling the material parameters and externally applied magnetostatic field, the performance of acoustical and polaron mode-induced optical parametric amplifiers may be improved. It is expected that a cheaper efficient optical parametric amplifier can be fabricated using [Formula: see text]-InSb-CO2 system as the outcome of this research work.

EXPERIENCE OF ORGANIC-HYBRID COMPOSITION APPLICATION IN WATER SHUT-OFF <https://translate.academic.ru/water%20production%20restraining/ru/en/> TECHNOLOGY

Background Analysis of the field experience of using gel-forming compositions for water shut-off showed that their application efficiency is low. So the development and application of stable gel-forming compositions with an adjustable gelling time, with high strength characteristics, including those with both viscoelastic and viscoplastic properties, capable to form waterproof screens on the water filtration path. The authors reviewed the experience of using a promising organic hybrid composition based on the KOM-S reagent. Aims and Objectives. Testing a methodological approach to predicting technological efficiency, based on the use of hydrodynamic modeling of the process. Analysis of the organic-hybrid composition based on the KOM-S reagent field tests results in two wells confined to heterogeneous reservoirs of Kumkol field Cretaceous deposits. Results During the implementation of the technology of the use of organic-hybrid composition based on the KOM-S reagent, positive results were obtained, expressed as an increase in oil production due to a decrease in the wells water-cut. A methodology for predicting the technological efficiency of conducting water shut-off operations based on hydrodynamic modeling has been proposed and tested. The high convergence of the prediction results and the actual indicators of the technology efficiency got during the performance of the PGI was obtained.

The Use of Hydrodynamic Models in the Determination of the Chart Datum Shape in a Tropical Estuary

Estuaries are transitional environments with ideal conditions for port construction and navigation. They represent a challenge to hydrographic services due to the dynamics of the seabed and the tidal wave deformation. The bottom slope, the convergence of the channels, and the nonlinear effects produced by the bottom friction produce variation in both the tidal range and the location of the chart datum (CD). In this study, sea level data series obtained from the nodes of the mesh of a hydrodynamic model (virtual tide gauges) were used to calculate the harmonic constituents, form factor, asymmetry, and estuary type. The final chart datum surface, obtained from the hydrodynamic model, was used to determine the separation values between zones and also the number of tidal zones in an estuarine system. It was found that in a complex hydrodynamics scenario, the use of the ellipsoidal referenced surveying (ERS) method is more convenient than traditional tidal zoning survey. In the ERS method, once the CD model is complete, it must be attached to the ellipsoid directly. Finally, the variation of the CD in different scenarios (due to anthropogenic action) was assessed.

Aerodynamic Errors of the Systems Aimed at Measuring the Static Pressure of an Aircraft in the Sliding Modes of Flight

We propose mathematical models of errors of the onboard measurements of static pressure of an aircraft in the sliding modes of flight based on the use of hydrodynamic models of flow around thin bodies. We also analyze and estimate the schemes of location of Pitot static probes traditionally used in the aviation practice, as well as the algorithms intended for the compensation of errors in the calculators of air-data systems. The results of determination of the component of aerodynamic error in the sliding modes of flight are presented. The accumulated data have been obtained in the course of flight tests of numerous transport aircrafts.

Assessing the Hydrogeomorphic Effects of Environmental Flows using Hydrodynamic Modeling.

Water managers are increasingly using environmental flows (e-flows) as a tool to improve ecological conditions downstream from impoundments. Recent studies have called for e-flow approaches that explicitly consider impacts on hydrogeomorphic processes when developing management alternatives. Process-based approaches are particularly relevant in river systems that have been highly modified and where water supplies are over allocated. One-dimensional (1D) and two-dimensional (2D) hydrodynamic models can be used to resolve hydrogeomorphic processes at different spatial and temporal scales to support the development, testing, and refinement of e-flow hypotheses. Thus, the objective of this paper is to demonstrate the use of hydrodynamic models as a tool for assisting stakeholders in targeting and assessing environmental flows within a decision-making framework. We present a case study of e-flows on the Rio Chama in northern New Mexico, USA, where 1D and 2D hydrodynamic modeling was used within a collaborative process to implement an e-flow experiment. A specific goal of the e-flow process was to improve spawning habitat for brown trout by flushing fine sediments from gravel features. The results revealed that the 2D hydrodynamic model provided much greater insight with respect to hydrodynamic and sediment transport processes, which led to a reduction in the recommended e-flow discharge. The results suggest that 2D hydrodynamic models can be useful tools for improving process understanding, developing e-flow recommendations, and supporting adaptive management even when limited or no data are available for model calibration and validation.

Time of concentration for large catchment based on hydrodynamic modelling

Flood mitigation design requires accurate computation of discharge at any interest location to sustain the protection level. The design flood hydrograph generates from rainfall runoff model which used unit hydrograph method depends on the time of concentration (Tc) of the catchment. Common factors which influence Tc are the catchment properties including length, slope, soil properties and surface cover. However, when dealing with large catchment, more complex factors which also requires attention are the rainfall intensity, catchment wetness and initial water in the channel due to rain prior to the storm event. For large catchment, the travelling time which govern the Tc is more dominant in the channel rather than on the soil surface. Since water flowing in the river channel is unsteady and nonuniform, the use of Manning formula is inappropriate. This paper explains the application of hydrodynamic modelling approach to determine Tc for large catchment with long river channel. A hydrodynamic river model for Sg Relai, Kelantan with area of 460 km2 and covering 90 km distance was developed using InfoWorks ICM. Results shown that as the rain intensity increased, the travelling time will be shortened. The traveling time also reduce when initial water level in the channel increase which indicate that Tc will reduce if the catchment already received some rainfall prior to the storm event. Based on this analysis and results, the use of hydrodynamic model as part of the rainfall runoff model is significant for large catchment to handle complex factor such as wide range of rainfall intensity, spatial effect and catchment wetness.

Mathematical modeling for the management of the carrying capacity of aquaculture enterprises in lakes and reservoirs

Abstract: Flooded areas of reservoirs and artificial lakes have been increasingly used for fish production; however, the waste generated by aquaculture has become a concern for the sustainable development of this activity. One of the main strategies adopted by management and regulatory agencies is the use of hydrodynamic models that calculate the carrying or nutrient load capacity of a particular water body and the effect of fish farming. These models are precise in the development of optimal strategies for feeding and waste calculation. This review paper addresses this topic and describes the methodology developed for the analysis and simulation of the carrying capacity for fish production, based on the integration of the Fish-PrFEQ nutritional bioenergetic model and the hydrodynamic model of Dillon & Rigler. This methodology allows evaluating the real contribution of aquaculture waste and assists in the planning and management of aquaculture in these aquatic environments, besides enabling and encouraging producers and the aquaculture industry to use fish food with better nutritional quality and lower environmental impact.

Uso de modelo hidrodinâmico para determinação da vazão a partir de medições de nível

RESUMO O uso de modelos hidrodinâmicos para a determinação das vazões em cursos d’água tem crescido nos últimos anos devido aos problemas relativos à utilização do método da curva-chave para monitoramento das vazões. Este trabalho tem por objetivo desenvolver um método para determinação das vazões em canais abertos utilizando algoritmos evolucionários multiobjetivos (NSGA-II) e medições de nível da superfície livre associadas a um modelo hidrodinâmico. Dados obtidos de ensaios em um canal experimental de laboratório foram utilizados para calibração e validação do modelo. O algoritmo de otimização NSGA-II apresentou excelentes resultados, obtendo-se coeficientes de Nash-Sutcliffe superiores a 0,99 tanto para a calibração quanto para a validação do modelo hidrodinâmico. As vazões calculadas pelo modelo hidrodinâmico apresentaram uma variação de até 150% para um mesmo nível quando comparadas às vazões estimadas pela curva-chave, o que demonstrou que o uso da curva-chave para medição de vazão em regime variável apresenta erros elevados.

Depth-dependent hydraulic roughness and its impact on the assessment of hydropeaking

Hydrodynamic river models in combination with physical habitat modelling serve as the basis for a wide spectrum of environmental studies. Larvae, juvenile and spawning fish, redds and benthic invertebrates belong to the biological groups most heavily affected by rapid flow variations as a consequence of peaking energy production, or “hydropeaking”. As these species find their preferential habitat to a great extent in shallow regions, high prediction accuracy for these areas is essential to substantiate the use of hydrodynamic models. In this paper, a new formulation for the depth-dependent roughness originating from the boundary layer theory is derived. The modelling approach is based on the concept of a dynamic, spatio-temporal Manning's roughness which allows for considerable improvement in the accuracy of stationary and highly transient hydrodynamic simulations in shallow river areas. In addition, the approach facilitates more effective model calibration, as it allows for the preservation of the roughness sublayer thickness as a single calibration parameter for the entire range of hydropeaking discharges. The approach is tested and validated on a 7.5km long stretch of a middle-size gravel river affected by hydropeaking. Model results using conventional constant roughness and the proposed dynamic roughness approaches are compared. The implications for the stationary habitat assessment and calculation of dynamic hydropeaking parameters are analysed as well.

Can We Trust Hydrodynamic Models to Determine the Bilayer Viscosity Experienced by Transmembrane Proteins?

Although the measurement of molecular mobility in bilayers is relatively straightforward, the influence of the nature of the bilayer on the diffusing molecule i.e. the viscosity of the bilayer is delicate and not well understood.It is unclear if the viscosity sampled by the diffusing micron size gel structure is a measure of the nanoscopic viscosity of the bilayers experienced by much smaller proteins. Indeed for transmembrane proteins, theoretical considerations make questionable the use of hydrodynamic models to fit experimental data since the diffusing particle is about the same size as the particles composing the fluid in which it is diffusing.We will present partial answers to questions that are still open in this context:- Do we observe viscosity changes from the value of macro-viscosity to the nano-scale and if it is so for what length-scale we observe a crossover from nano to macro?- What is the relation between nanoviscosity determined from the diffusion of nanoprobes such as proteins and macro-viscosity obtained from the diffusion of gel domains?- And finally how nanoviscosity, extracted from Fluorescence Recovery After Photobleaching (FRAP) and hydrodynamic models, compares to the nanoviscosity measured with molecular rotors by Fluorescence Lifetime Imaging Microscopy (FLIM)?