New Trends in PHOENICS Development Message for the

New Trends in PHOENICS Development Message for the Tokyo PHOENICS-User Meeting from Brian Spalding CHAM-Japan November, 2011 Welcome PHOENICS was first released as a commercial CFD code in London, in October 1981. A year later it was introduced to Japan by CRC, and Japanese Users of PHOENICS have been, since then, among the most ingenious and productive in the world. I therefore welcome this opportunity to address them and to explain in what ways, thirty years after its birth, PHOENICS is still developing, in response to the changing needs of its users.

New Trends in PHOENICS Development Message for the Tokyo PHOENICS-User Meeting Summary CHAM-Japan November, 2011 The needs of PHOENICS users are not all the same. In the past, CHAM has tried to satisfy all by means of a single data-input module, the VR-EDITOR, operating in graphical interactive mode. There are two drawbacks: 1. VRE presents too many choices for some users; and 2. it cannot activate all PHOENICS capabilities. Now therefore CHAM has added new input procedures which meet the differing needs of five different classes of user. These will now be described.

New Trends in PHOENICS Development Recognising five different groups of users: 1. those needing Gateways CHAM-Japan November, 2011 PHOENICS is a General-Purpose package; but most of its users have special purposes. User Group 1 wants easy-to-use simulation-and-design software for particular processes, e. g. : • heat exchangers (shell-and-tube, plate, air-cooled… ) • chemical reactors (CVD, stirred-tank, fluidised-bed. . . ) • environmental flows (wind-farm, city pollution, fires… ) • pumps and fans (gear-wheel, bladed, piston-cylinder. . . ) To this group CHAM offers specialpurpose stand-alone packages, accessed through application-specific Gateways.

New Trends in PHOENICS Development Recognising five different groups of users. CHAM-Japan (continued) November, 2011 2. Gateway Creators CHAM has itself created several gateways; and it will create any more which customers commission. But users of Group 2 are those who wish to create their own. To this group CHAM offers: • Examples of parameterised relational-data-input files; • explanations of these, and assistance, in the creation of new ones. • PRELUDE, which automatically converts these into Gateway packages which exactly suit the needs of the defined Group-1 users.

New Trends in PHOENICS Development Recognising five different groups of users (continued): 3. Those requiring new features CHAM-Japan November, 2011 Gateways enable users easily to access existing features of PHOENICS; but Group-3 users wish involve features which do not yet exist, for example: • unusual geometries not fitting structured grids; • materials with unusual thermo-physical properties; • never-before-tried turbulence models; or • novel equation-solving algorithms. To this group CHAM offers: • In-Form which adds new features without new Fortran or C coding; • advice and assistance for those who request it; • a library of cases for copying.

New Trends in PHOENICS Development Recognising five different groups of users (continued) 4. students and teachers CHAM-Japan November, 2011 PHOENICS can be used for learning about fluid mechanics, heat transfer, chemical reaction, solid mechanics and their engineering and environmental effects. For Group-4 members, i. e. students and teachers, CHAM offers: PHOENICS-For-Teaching, which comprises: • an extremely-simple interface; • a teacher mode which creates cases to be run; • a student mode which facilitates running of cases; • automated calculation and display of results; • multi-language text capability; • an organisational framework which enables contributors to collaborate internationally.

New Trends in PHOENICS Development Recognising five different groups of users (continued) 5. Already-experienced users CHAM-Japan November, 2011 Experienced users of PHOENICS may require no fundamental changes. As Group 5 they desire only that: • all familiar features should continue to exist; • changes should be only in greater speed of operation, richness of options, freedom from failures. To this group CHAM offers: • Continued development to ensure that the VR Editor, the Earth solver, the VR Viewer, PHOTON. POLIS, Parallel Operation, etcetera remain in use and are improved in detail. • Free-of-charge support to maintained users.

New Trends in PHOENICS Developments relating to Group 1: An example: the hen-house gateway CHAM-Japan November, 2011 • Let us suppose that the task is to predict air temperature, humidity and composition within a hen-battery building. • It is a CFD problem; so PHOENICS can be used to solve it. But how? • Input data include the geometry (what is where); the production rates of heat and pollutant from each cage; the air-supply rate and temperature. • Free (gravity-induced) convection is as important as forced convection.

CFD for the hen-house Ease of use is essential CHAM-Japan November, 2011 New Trends in PHOENICS Development . • Specialists in the animal-productionenvironment know little about CFD. They need programs devised especially for them. • Data input should be made easy, so as to save time and minimise mistakes. • Simulation results should be presented in a way which makes them easy to inspect and interpret.

New Trends in PHOENICS Development The CFD-Gateway concept; What a hen-house gateway might look like CHAM-Japan November, 2011 Picture of Gateway menu panel with part of a battery of chickencages in its graphics window. Button rows are standard for all Clicking on items in the ‘object tree’ reveals what is gateways. specific to this gateway. .

New Trends in PHOENICS Developments relating to Group 1: input data which the user will supply CHAM-Japan November, 2011 The Gateway user will supply, via menu boxes, the data which he knows about e. g. : • size, number and arrangement of cages; • location, temperature and flow rate of air supply; • attributes of chickens (heat output, oxygen consumpton, air-pollution rate). The Gateway user will not be asked to choose: • turbulence models, • grid type or fineness; • sweep number; • relaxation and other numerical parameters. The Gateway creator (User-Group 2) will have already built choices into the Gateway-design script.

New Trends in PHOENICS Development The CFD-Gateway concept; Looking at the results CHAM-Japan November, 2011 After its user is satisfied with the input data, clicking the ‘run’ button launches the simulation and displays results as velocity vectors (right) or contour displays (left) on accordance with pre-set orders, or the user’s menuexpressed wishes. The left-hand picture shows the SMEL (odour) contours.

New Trends in PHOENICS Development The CFD-Gateway concept; What the Group-1 user would learn CHAM-Japan November, 2011 Printed numerical results of interest to the user might include: • locations and maximum values of temperature, airpollutant, etcetera; • electric power and heat input needed for specified conditions. By varying the input conditions and observing the changes in results, the user would thus be enabled to determine how to optimise hen-house design and operation. Thus the animal-production specialist could become, without expensive training, a user of PHOENICS and CFD.

New Trends in PHOENICS Development Second user Group: The Gateway Creators CHAM-Japan November, 2011 Users of Group 1 are able to benefit from CFD when suitable PHOENICS Gateways have been prepared for them by someone else. By whom? By Group-2 users, who have learned how to create Gateways. Managers please note: Personnel for Groups 1 and 2 utilise different skills, and convey different benefits. A well-balanced team requires persons of both kinds.

Developments relating to User Group 2: CHAM-Japan November, how to create the hen-house gateway New Trends in PHOENICS Development 2011 To create a new gateway, one need not start from scratch; for the PRELUDE package exists, with ready-touse general framework and customising tools. Here is shown its standard top-menu bar. These provide the frequently-required functions of opening cases, introducing or deleting objects, selecting them for attribute modification, running simulation calculations, etcetera. Tutorials exist which explain these.

New Trends in PHOENICS Developments relating to Group 2: Objects and their attributes CHAM-Japan November, 2011 Here is shown an object tree which might be created for a hen-house gateway. Clicking on an item enables its attributes to be reviewed, and edited if need be. These items control results-display items, viz stream-lines; and ‘cutting planes’ for contours and vectors; and these the in-and outflow of ventilating air. Here are the stored and solved-for 3 D variables. Note that SMEL, of which chickens are a source, is one of them.

New Trends in PHOENICS Developments relating to Group 2; Inserting an array of cage objects CHAM-Japan November, 2011 It would be tedious to introduce the cages one by one; so PRELUDE offers an ‘array’ facility seen below. Note that expressions can be entered. Here ‘shed’ is the (highlighted) name of the array. ‘Cage’ is the name of the object arrayed.

New Trends in PHOENICS Development Comparison of VR-Editor and PRELUDE The PHOENICS VR Editor facilitates the setting up only of single-instance flow-simulation scenarios. For example, only numbers can be typed into its menu boxes, thus; but not expressions as in PRELUDE: VRE can display scenarios created by PRELUDE. But it lacks PRELUDE’s arrayspecification feature. PRELUDE. is therefore the preferred user interface for PHOENICS. CHAM-Japan November, 2011

New Trends in PHOENICS Developments relating to Group 2: what the Gateway-creator must do CHAM-Japan November, 2011 Just as VRE receives instructions from Q 1 written in PHOENICS Input Language (i. e. PIL), PRELUDE receives instructions from Q 3 written in PRELUDE Script Language (i. e. PSL). Group-2 users can learn PSL, and so write Q 3 files: or they can express their needs in parameterised Q 1 (i. e. PIL) files. Then PRELUDE can translate these into Q 3 files. Therefore Group-2 users need not learn PSL. Tutorials explain how to write parameterised Q 1 s; and there exist input-file-library examples and a power-point presentation.

New Trends in PHOENICS Developments relating to Group 2: data input CHAM-Japan November, 2011 How PRELUDE, Q 1, Q 3, VRE, etc fit together is shown below. Gateway creators express choices of turbulence models and numerical parameters via PIL in Q 1. They must also make wise choices about whether (or when) to use Space-Averaged or Detailed-Geometry CFD, both of which PHOENICS can supply. What are SACFD and DGCFD? See next slide.

Space-Averaged- and Detailed. Geometry CFD for heat exchangers New Trends in PHOENICS Development SACFD Tubes in a heat exchanger are too numerous for DGCFD to be used for the whole equipment; so formulae for volumetric heat transfer are used, derived from CHAM-Japan November, 2011 DGCFD results of DGCFD applied to parts of the tube bundle. The DGCFD results are obtained first. Then the results are parameterised for use later in SACFD.

New Trends in PHOENICS Development DG-CFD as the extrapolator from experimental data CHAM-Japan November, 2011 Question: But there exist experimental data for volumetric heat -transfer and friction coefficients of tube bundles, as shown on the right. Why not use them? Answer: They should be used; but there are never enough of them; and they seldom reveal the effects of, say, property variations with temperature. So they are best used for calibrating DG-CFD simulation models.

New Trends in PHOENICS Development SA- and DG-CFD; applied to the hen house CHAM-Japan November, 2011 Combined SA and DG can be applied to henhouse simulation simply by setting the array parameters to 1, 1, 1, with the result on the right: Now all the computational cells can be concentrated in the smaller domain surrounding the single cage; so transfers of heat, matter and momentum from hen to air can be more accurately simulated. Doing so at various Reynolds numbers and wind angles allows formulae to be developed which can be used in whole-hen-house SA-CFD simulations.

New Trends in PHOENICS Development Detailed-geometry CFD; The pecking chicken, 1. PRELUDE can also be used for moving objects Here is a chicken, with the detailedgeometry grid set up for a timedependent simulation. CHAM-Japan November, 2011

New Trends in PHOENICS Development Detailed-geometry CFD; The pecking chicken, 2. PRELUDE enables the motion of the chicken to be prescribed by way of formulae. Here is the formula to be used for describing its periodic pecking motion. The PHOENICS MOFOR (i. e. MOving. Frame- Of Reference) technique is activated. CHAM-Japan November, 2011

New Trends in PHOENICS Development Detailed-geometry CFD; The pecking chicken, 3. CHAM-Japan November, 2011 Here is an animated view of some results of simulation. Note the airvelocity vectors and surface pressures. This shows (more for entertainment than necessity) what can be done with detailed-geometry CFD; hen-house designers need not go so far!

New Trends in PHOENICS Development The Moving-Frame-of Reference Technique; some details CHAM-Japan November, 2011 MOFOR consists of two features, namely: (1) description of the motion; and (2) Creating the response of the fluid to that motion. The first uses a technique borrowed from the motionpicture industry (‘Titanic’, ‘Babe’): a ‘MOF file’ is generated, as shown on the next slide. It dictates the translations, rotations and corresponding velocities and accelerations of torso and limbs. The second exploits whatever source-and-sink mechanism is present in the underlying CFD solver (here, of course, PHOENICS).

New Trends in PHOENICS Development The MOF file generated by PRELUDE for the pecking hen CHAM-Japan November, 2011 Below is the first part of the MOF. Below it are the corresponding tables of numbers which represent the coordinates of the body and limbs at a { succession of times. # : : q 1 object chookb # Prelude generated MOF file using time dependent degrees of freedom. HIERARCHY UNITS METRES ROOT Cham { JOINT world { # : : groupobject world OFFSET 0. 000000 JOINT chicke { # : : groupobject chicke OFFSET 0. 500000 0. 000000 JOINT chookbcore OFFSET 0. 000000 0. 043844 # : : localrot chookb JOINT chookb # localaxis locrot 0 { OFFSET 0. 000000 0. 2050000 0. 200000 CHANNELS 1 Xrotation End Site } }

New Trends in PHOENICS Development CFD for hen-house simulation: summary of the argument. CHAM-Japan November, 2011 It has been argued, with exemplification, that: • Current CFD techniques are adequate for the simulation of flow of air and pollutants in hen-houses. • Both space-averaged and detailed-geometry techniques are needed. • Even moving-object scenarios can be simulated. This example has shown how Group-2 users of PHOENICS can create Gateways for Group-1 users. Who may these Group-2 Users be? CHAM, or CHAM-J, personnel of course; but also any user who is willing to learn PIL.

Other existing Gateways: SHELLFLO CHAM-Japan November, 2011 New Trends in PHOENICS Development SHELLFLO assists designers of shell-and-tube heat exchangers to understand the flow inside their equipment. Here the x, y and z locations of a baffle in a shell-and-tube heat exchanger are being fixed so as always to fit the shell. Volumetric frictionand heat-transfercoefficient formulae, in terms of local Reynolds and Prandt Number can be input in this manner.

New Trends in PHOENICS Development Other existing Gateways: The Virtual Wind. Tunnel, VWT 1 CHAM-Japan November, 2011 Velocity vectors around a sphere, in a structured grid

Other existing Gateways: The Virtual Wind. Tunnel, VWT 2. CHAM-Japan November, 2011 New Trends in PHOENICS Development Velocity vectors around a sphere in an unstructured grid PRELUDE can display results for both structured and unstructured grids. It uses the public-domain VTK file format.

New Trends in PHOENICS Development Other existing Gateways: Terrain CHAM-Japan November, 2011 The Terrain Gateway facilitates simulation of wind flow, air pollution and fire spread over natural and human-built territories. Thereafter users load terrain-description files, wind profiles, pollution sources, choose grid type, etc. Then PRELUDE write Q 1, activates EARTH and displays results. Examples follow. .

New Trends in PHOENICS Development Other existing Gateways: Terrain CHAM-Japan November, 2011

New Trends in PHOENICS Development Other existing Gateways: Terrain CHAM-Japan November, 2011 Here PRELUDE displays other aspects of the same case. It can handle both structured and unstructured grids.

New Trends in PHOENICS Development Other existing Gateways: Terrain CHAM-Japan November, 2011

New Trends in PHOENICS Development Other existing Gateways: Terrain CHAM-Japan November, 2011

New Trends in PHOENICS Development Other Gateways under consideration SHELLFLO considers only the shell of single-pass shell-and-tube heat exchangers. Many more configurations require study (see right); and with boiling and condensation also. For which would there be customers in Japan? CHAM would welcome Japanese collaborators in new-gateway creation. CHAM-Japan November, 2011

New Trends in PHOENICS Development User-Group 3; Users with new problems of their own to solve CHAM-Japan November, 2011 When no Gateway exists, and the problem to be solved has novel elements, users need to find for themselves what PHOENICS facilities to use. Three examples will be referred to: 1. Data-centre cooling 2. Air-cooled condensers 3. Populational CFD

New Trends in PHOENICS Development User-Group 3: The Data-Centre problem CHAM-Japan November, 2011 Its nature is ‘simply’ Heating and Ventilating. The difficulty lies in its magnitude. Many computer cabinets and heat-extraction units are crowded together. . But a parameterised Q 1, linked to Excel, does the job.

User-Group 3: The Data-Centre solution CHAM-Japan November, 2011 New Trends in PHOENICS Development PHOENICS provides graphical and numerical results. The easy-to-modify input-file structure allows centre managers to optimise the location of equipment units, and to detect dangerous excessive-heating locations. The data-input package was constructed by CHAM UK’s consultancy team for its own use; but it can be leased by others. In the future, a Data-Centre Gateway may be created. . .

New Trends in PHOENICS Development User Group 3: The air-cooled-condenser problem Air-cooled steam condensers involve three phases: air, steam and water, and three geometrical dimensions. There are size disparities between the total air space and the thin gaps between tube fins. The air occupies the whole space; but steam and water only a small fraction of it. Unthinking reliance on the VR Editor would lead to expensive and still inaccurate computations. CHAM-Japan November, 2011

New Trends in PHOENICS Development User Group 3: The air-cooled-condenser problem 2 CHAM-Japan November, 2011 The flow inside the tubes of the bundle may be complex; yet it greatly affects performance; and therefore must be simulated. In cold weather, ice may form within the tubes. A computer model should predict its effect. The tube inclination will entail maximum ‘numerical-diffusion’ inaccuracy if the easiest-to-use structured Cartesian grid (see left) is used.

New Trends in PHOENICS Development User Group 3: The air-cooled-condenser solution, 1 CHAM-Japan November, 2011 Flexible PHOENICS permits unconventional solutions, e. g. represent one volume twice, in different parts of the grid. This solves the numericaldiffusion problem. It also allows one set of variables to serve for two materials, viz air in one part and H 2 O in the other. Two extra additional grid parts would allow steam and condensate to have distinct velocities and temperatures. The heat transfers between the air, steam and water can be easily expressed by In-Form statements in the Q 1.

New Trends in PHOENICS Development User Group 3: The air-cooled-condenser solution, 2 CHAM-Japan November, 2011 Both Space-Averaged and Detailed-Geometry CFD are needed; for the handbook data for finned-tube-bundle heat transfer and pressure drop are unreliable. The PHOENICS PARSOL technique (see above) is very suitable for the DGCFD part of this problem. PIL+In-Form proved powerful enough: • to link object position and grid distribution to tube angle, length and diameter; and • to enable thermodynamic properties of steam/air/water to be computed via statements in Q 1.

New Trends in PHOENICS Development User Group 3: The air-cooled-condenser: conclusions CHAM-Japan November, 2011 The work, still in progress at CHAM UK, has proved the multi-part grid to be practicable. It is even better when inclined as shown here. 3 D effects caused by the circular-fan shape are small. Those caused by the steam and condensate pipes are larger. It is too early to create a Gateway.

New Trends in PHOENICS Development User Group 3: Populational CFD CHAM-Japan November, 2011 ‘Populational CFD’ treats multi-phase and singlephase turbulent flows in a similar manner. In my opinion it represents the new frontier of CFD research. PHOENICS is the computer code which is mainly being used for its investigation

New Trends in PHOENICS Development How Populational CFD differs from Conventional CFD, 1 CHAM-Japan November, 2011 Both discretise space and time by use of grids of cells, structured or unstructured. Both solve algebraic mass-, momentum - & energy -conservation equations by iterative numerical methods Both take account of (1) sources, (2) diffusion, (3) convection and (4) time-dependence.

New Trends in PHOENICS Development How Populational CFD differs from Conventional CFD, 2 CHAM-Japan November, 2011 Conventional CFD accounts for the four processes just listed; but Populational CFD accounts for two more, namely: (5) Merging, by way of collision, coupling-and-splitting or engulfment, engulfment which influence turbulent combustion, and (6) differential (i. e. selective) convection, which influences buoyant and swirling flows.

New Trends in PHOENICS Development One aspect of populational CFD Proportion-of-time calculations CHAM-Japan November, 2011 Calculated proportions of time that temperature lies above or between given limits in flow behind a squaresectioned obstacle in a non-uniform temperature field. A two-dimensional LES simulation was judged sufficient for the present purpose. Typical instantaneous temperature contours are on the left. On the right are contours of computed PTA_0. 5, i. e. proportion of time spent above a temperature midway between highest and lowest.

New Trends in PHOENICS Development Concluding remarks about populational CFD CHAM-Japan November, 2011 For more on this research-frontier subject see “Mapping Turbulent Combustion” at: http: //www. cham. co. uk/lectures. php

New Trends in PHOENICS Development PHOENICS-for-Teaching. PFT: User-group 4 CHAM-Japan November, 2011 Professors teach students about fluid dynamics, heat transfer, solid mechanics, etc. , by lectures and laboratory classes. PHOENICS-for-Teaching is designed to help them. PRELUDE and VR-Editor present too many choices for this User Group 4. So PFT’s simple-as-possible GUI focusses on one topic at a time, for example:

New Trends in PHOENICS Development PHOENICS-for-Teaching. PFT: The Main Ideas CHAM-Japan November, 2011 What is to be taught can be classified as: • Subjects, e. g. Heat Transfer • Sub-divisions, e. g. Convective heat transfer • Further sub-divisions, e. g. extended-surfaces • particular topics, e. g. finned tube In cross-flow Professors, and text books, teach the classification and classical methods of analysis. PHOENICS-for-Teaching assists them at the particulartopic level. PFT also handles what classical analysis can not, viz. : • practical geometries; • temperature-dependent properties; • complex interactions between processes.

PHOENICS-for-Teaching. PFT: The simple user interface CHAM-Japan November, 2011 New Trends in PHOENICS Development The interface describes the case; then allows data input.

New Trends in PHOENICS Development PHOENICS-for-Teaching. PFT: The user interface CHAM-Japan November, 2011

PHOENICS-for-Teaching. PFT: The user interface concluded CHAM-Japan November, 2011 New Trends in PHOENICS Development And finally Thereafter the student presses ‘run the simulation’; then views the results graphically, by means of macro-driven PHOTON or VIEWER; or in alphanumeric form. What could be simpler?

New Trends in PHOENICS Development PHOENICS-for-Teaching. PFT: A future collaborative development CHAM-Japan November, 2011 The PHOENICS-for-Teaching Project has just begun. Therefore only a few topics have been dealt with so far. However, the structure exists; and the way ahead is clear; so progress may be rapid. CHAM will supply PHOENICS-for-teaching free-ofcharge to collaborators who agree to make their files available to all teachers and students world-wide.

New Trends in PHOENICS Development User Group 5. Four developments which may interest experienced users of PHOENICS CHAM-Japan November, 2011 1. A PARSOL and Parallel problem solved. Parallel PHOENICS works by splitting a large domain into many slightly-overlapping sub-domains and assigning a processor to each. When PARSOL is used, neighbouring processors sometimes disagree about cell-cutting in the over-lap region, causing execution failure. The solution has been: “Let them disagree; but let the second processor accept the first processor’s decision. ” That’s easily said; but hard to implement in coding. Nevertheless, the problem has been finally solved.

New Trends in PHOENICS Development User Group 5. Four developments which may interest experienced users of PHOENICS CHAM-Japan November, 2011 2. A welcome discovery about GCV For wind-farm simulation, users of Windsim, the userinterface package for which PHOENICS is the CFD ‘engine’, have often encountered divergence. Windsim uses a BFC grid to describe the terrain; and had used the settings: MIGAL=T; GCV=F. CHAM then advised: set MIGAL=F; GCV=T; whereupon convergence was obtained unfailingly. The conclusion? GCV (General Colocated Velocities) should always be selected for BFC problems. An objection is: the GCV solver has not been ‘parallelised’. This omission is being remedied.

New Trends in PHOENICS Development User Group 5. Four developments which may interest experienced users of PHOENICS CHAM-Japan November, 2011 3. Automatic convergence Wind-farm (and general terrain) problems are comparatively simple (small height/width ratio; fixedpressure at sky); so procuring convergence is not hard. For general flows, CHAM’s CONWIZ automaticconvergence promoter is usually effective; but it is being improved in a current study (not yet complete). Findings so far are: • Never use false-time-step relaxation • ‘Residuals’ values are unreliable tests of convergence. • Small LITER for velocities (even PBP! are advisable. • Optimal LITER(P 1) is of ten less than 100. • Further systematic studies are needed. • Guaranteeing convergence is the duty of CHAM.

New Trends in PHOENICS Development User Group 5. Four developments which may interest experienced users of PHOENICS CHAM-Japan November, 2011 4. Improved graphical-display features Such improvements are too numerous to list here. Therefore I conclude with one so small that it may escape attention: controlling GXMONI line thickness. For many years GXMONI lines were one-pixel thick. Now, at last, user can change thickness via cham. ini. The image on the right shows three monitor plots, with Line. Width = 10, 4 and 2.

New Trends in PHOENICS Development: a final summary CHAM-Japan November, 2011 PHOENICS appears now differently to each user group. 5. Traditional users see it as changing only in detail and in richness of options (structured/unstructured, etc). 4. Student & teacher users see an easy-to-handle mini. PHOENICS, which does what they need and no more. 3. Innovative users at the frontier of CFD and its applications see PHOENICS as a box of power tools; but they may need help in using them. 2. Gateway creators, learning to write parameterised Q 1 files, automated by PRELUDE, assist their ‘frontline’ colleagues. 1. Then the latter can be productive and trouble-free.